Productivity · Weekend build
Build your own Adobe Acrobat Pro
Merge, split, rotate, compress, and redact—without an account maze. Adobe Acrobat Pro charges $20–$30 per month — that’s $240–$360 a year — for something you can replace with focused software of your own. Here is the honest scope, the honest timeline, and the exact prompt to hand your coding agent.
Who this replacement is for
This build targets one person handling ordinary non-sensitive PDF chores. The goal: perform a small set of predictable PDF operations locally and download the result. If you need more than that, keep paying — the point of building it yourself is owning a tool shaped exactly like your workflow, not re-implementing a venture-funded roadmap.
Same build, different logo: this v1 also replaces Smallpdf, iLovePDF, PDF Expert and DocHub — they all solve the same core job.
How long it actually takes
One number would be a lie, so here are three. Each tier is a real, usable product — pick the one that matches how much of Adobe Acrobat Pro you actually use.
| Estimate | What you get |
|---|---|
| 8 hours | merge, split, rotate pdf pages |
| 3 days | compression presets, true redaction, thumbnails, local processing |
| 3 months+ | ocr, e-signatures, form editing, a real pdf engine — the part you should probably skip |
What a minimal Adobe Acrobat Pro alternative needs
- drag-and-drop PDF queue with page thumbnails
- merge, reorder, rotate, extract, and delete pages
- compression presets with before-and-after size
- permanent rectangle redaction with explicit preview
- download result and clear all local working data
Data model
local DocumentJob, PageSelection, RedactionMark, ExportResult
Integrations
browser File API, PDF processing library, Web Workers
Capability context
Astro, Alpine, Browser API
The guardrail
Process documents locally by default, never fake redaction with overlays, and clearly warn when a file has signatures or unsupported encryption.
Deliberate non-goals
Do not add cloud storage, OCR, e-signatures, legal compliance claims, accounts, or collaborative review.
The complete build prompt
Copy this into your coding agent of choice. It is scoped for a useful v1 — journeys, screens, business rules, data model, security, tests, and acceptance scenarios included. Pick your stack:
You are building a production-ready software product named “Paperknife”, a deliberately focused alternative to Adobe Acrobat Pro. Build a complete, usable vertical slice—not a landing page, static mockup, or disconnected collection of components. WORKING AGREEMENT Before writing implementation code, produce a short technical plan that names the routes or pages, server actions or endpoints, data tables, important state transitions, authorization boundaries, background jobs, and external adapters. Resolve contradictions in favor of the narrow audience and non-goals below. Prefer a small, legible architecture over speculative abstraction, but do not omit persistence, validation, error handling, or tests. PRODUCT BRIEF Primary user: one person handling ordinary non-sensitive PDF chores. Primary outcome: perform a small set of predictable PDF operations locally and download the result. Product principle: optimize the exact workflow below instead of copying the full breadth of Adobe Acrobat Pro. A first-time user should understand what to do from the interface itself, without a tour or documentation. END-TO-END USER JOURNEYS Implement all of these flows through the real interface and persistent data layer: 1. The user drops three PDFs, reviews their page thumbnails, reorders and rotates pages, removes an unwanted page, and downloads one merged document. 2. The user opens a large PDF, selects a compression preset, compares estimated and final size, and downloads the smaller result without uploading it. 3. The user draws redaction rectangles, previews the permanently flattened output, confirms the warning, downloads it, and clears all working data. SCREENS AND INFORMATION ARCHITECTURE Build these as coherent responsive views. Each screen must specify its primary action, secondary actions, visible status, validation feedback, empty state, loading or pending state, success confirmation, and recoverable failure state. 1. Job start: operation choices, file drop zone, supported limits, local-processing reassurance, encryption warning, and readable validation errors. 2. Page organizer: thumbnails, source document, order, rotation, selection, extract and delete controls, undo, zoomed preview, and processing state. 3. Compress and redact: preset or redaction tools, visible marks, irreversible-action explanation, before-and-after preview, and unsupported-feature warning. 4. Export: filename, page count, exact output size, download, start over, clear-working-data action, and failures that preserve the source selection. CORE CAPABILITIES 1. drag-and-drop PDF queue with page thumbnails 2. merge, reorder, rotate, extract, and delete pages 3. compression presets with before-and-after size 4. permanent rectangle redaction with explicit preview 5. download result and clear all local working data DETAILED BEHAVIOR AND BUSINESS RULES Treat these as server-enforced product requirements, not interface suggestions: 1. Keep source bytes and all intermediate documents in browser memory or isolated temporary storage and clear them on explicit reset, tab close where possible, or bounded expiry. 2. Parse PDFs with a maintained library inside a worker, cap file and page counts, reject unsupported encryption safely, and never execute embedded actions or scripts. 3. Implement redaction by removing or rasterizing covered content in the exported document; an annotation or opaque visual overlay never counts as redaction. 4. Build every result from an immutable operation list so undo is safe and failed processing cannot corrupt the original input. DATA MODEL AND LIFECYCLE Design a small relational schema centered on local DocumentJob, PageSelection, RedactionMark, ExportResult. Before implementing it, document: 1. Each table’s purpose, primary key, ownership or tenant boundary, timestamps, status fields, and important attributes. 2. Foreign keys, uniqueness constraints, check constraints, indexes needed by the named screens, and transaction boundaries for multi-record changes. 3. The allowed lifecycle or state transitions, who may trigger each transition, which transitions are terminal or reversible, and what audit history must remain immutable. 4. Archive, retention, and deletion behavior, including what happens to dependent records and external files. 5. Idempotency strategy for submissions, jobs, imports, notifications, webhooks, or retries where applicable. Use migrations rather than ad-hoc schema creation. Store time instants consistently and retain named timezone context whenever local schedules or dates matter. Never rely on a counter, disabled button, or client-side check to preserve a business invariant. USERS, AUTHENTICATION, AND PERMISSIONS Implement only the roles required by the stated audience. Make the ownership and visibility model explicit before coding. Enforce authorization in every server-side query and mutation, including search, exports, attachments, live updates, and guessed URLs—not merely by hiding controls. Use secure session defaults, protect state-changing requests, and provide an understandable signed-out, expired-session, and forbidden state. Seed distinct users when multiple roles are required so permissions can be demonstrated and tested. INTERACTION AND VISUAL DIRECTION The product should feel fast, calm, focused, and credible rather than like a generic admin template. Use a clear visual hierarchy, restrained color, readable typography, generous hit targets, and consistent placement for primary actions. Start with server-rendered HTML and progressively enhance only the interactions that benefit from it. The core workflow must remain understandable if enhancement fails. Start with server-rendered Astro pages and ordinary HTML forms. Use HTMX for form submissions, partial navigation, and server-driven updates, then Alpine.js only for small local browser state. The core workflow must remain understandable if either enhancement layer fails. Design mobile layouts intentionally instead of simply stacking desktop panels. Support keyboard navigation, visible focus, semantic landmarks, explicit labels, useful page titles, reduced-motion preferences, and screen-reader announcements for asynchronous results. Never use color alone to communicate state. Destructive actions require clear scope and confirmation; safe repeated actions should be idempotent. TECHNICAL DIRECTION Build this version with the AHA stack: Astro for routing, layouts, and server-rendered pages; HTMX for interactions that benefit from HTML fragment responses; and Alpine.js for small, local interface state. Prefer Cloudflare D1 for relational persistence, R2 for object storage, Workers for server endpoints and scheduled work, Durable Objects only for coordinated real-time state, and Workflows or Queues for durable background jobs—but only when the product requirements call for them. Keep domain rules in testable server-side modules instead of route handlers or UI components. Separate persistence, external providers, and background work behind small interfaces without building a framework. Prefer ordinary HTML forms and URLs for durable navigation; use optimistic interaction only when failure can be reconciled clearly. The product brief currently identifies Astro, Alpine, Browser API as capability context. Preserve any required native, browser-only, edge, storage, real-time, or background-processing capability through a narrow adapter appropriate to the selected framework. If the core workflow genuinely requires native or browser APIs, keep that runtime as the primary execution surface rather than simulating inaccessible capabilities or inventing an unnecessary web surface. Integrate with browser File API and PDF processing library and Web Workers. For every integration: - List required environment variables in an .env.example without real secrets. - Add a small adapter with timeouts, normalized errors, and a deterministic local fake or development path. - Verify inbound signatures and deduplicate provider events where supported. - Keep credentials server-side, encrypt long-lived provider tokens at rest, and redact secrets and sensitive payloads from logs. - Define retry, backoff, and idempotency behavior for any side effect that can be repeated. SECURITY AND PRIVACY Process documents locally by default, never fake redaction with overlays, and clearly warn when a file has signatures or unsupported encryption. Validate, normalize, and length-limit all untrusted input on the server. Escape rendered content by default, sanitize any intentionally accepted markup, rate-limit public or abuse-prone actions, and use private object storage plus short-lived authorized URLs for sensitive files. Collect the minimum personal data necessary for the named workflow. Document retention and deletion behavior. Add specific protections for the riskier surfaces in this app, such as uploads, redirects, outbound requests, email delivery, OAuth, webhooks, CSV import or export, and real-time connections. ACCEPTANCE SCENARIOS Automate these app-specific scenarios at the most appropriate level: 1. Given two supported PDFs, reorder and rotate produces a valid merged file in the exact previewed order while the originals remain unchanged. 2. Given an encrypted or malformed PDF, processing stops with a specific error and no partial output is offered as valid. 3. Given text underneath a confirmed redaction rectangle, extracting text from the exported PDF cannot recover the covered content. TESTING Add focused unit tests for state transitions, authorization predicates, normalization, date or money calculations, and other risky domain rules. Add integration tests for persistence constraints and each external adapter’s success, timeout, retry, and rejection paths. Add at least one browser-level test for every end-to-end journey above, including one small-screen viewport. Tests must use isolated data and run through a documented single command. OPERATIONS AND FAILURE RECOVERY Add structured server logs with request, job, or event correlation IDs but no secrets or unnecessarily sensitive data. Make failures actionable in both the interface and logs. Background work must expose pending, succeeded, failed, and retrying states where relevant; do not silently swallow errors. Include safe database migration and rollback guidance, seed data, backup and restore notes, external-data cleanup behavior, and a basic health or diagnostic path appropriate to the stack. DELIVERABLES Ship the working application, migrations, representative seed data, tests, .env.example, and a concise README. The README must cover prerequisites, local setup, environment variables, migrations, seed and test commands, deployment, integration setup, backup and restore, security decisions, and known limitations. Seed data should exercise the happy path plus at least one empty, failed, overdue, expired, archived, or permission-restricted state relevant to the product. DEFINITION OF DONE The app is complete when a fresh developer can follow the README, create and migrate the database, run the app, sign in as each relevant role, complete every named journey using real persisted data, refresh without losing state, recover from common failures, and use the core interface on phone and desktop. All acceptance scenarios pass, permission boundaries are covered by tests, and no core screen is left as a placeholder. NON-GOALS Do not add cloud storage, OCR, e-signatures, legal compliance claims, accounts, or collaborative review.
You are building a production-ready software product named “Paperknife”, a deliberately focused alternative to Adobe Acrobat Pro. Build a complete, usable vertical slice—not a landing page, static mockup, or disconnected collection of components. WORKING AGREEMENT Before writing implementation code, produce a short technical plan that names the routes or pages, server actions or endpoints, data tables, important state transitions, authorization boundaries, background jobs, and external adapters. Resolve contradictions in favor of the narrow audience and non-goals below. Prefer a small, legible architecture over speculative abstraction, but do not omit persistence, validation, error handling, or tests. PRODUCT BRIEF Primary user: one person handling ordinary non-sensitive PDF chores. Primary outcome: perform a small set of predictable PDF operations locally and download the result. Product principle: optimize the exact workflow below instead of copying the full breadth of Adobe Acrobat Pro. A first-time user should understand what to do from the interface itself, without a tour or documentation. END-TO-END USER JOURNEYS Implement all of these flows through the real interface and persistent data layer: 1. The user drops three PDFs, reviews their page thumbnails, reorders and rotates pages, removes an unwanted page, and downloads one merged document. 2. The user opens a large PDF, selects a compression preset, compares estimated and final size, and downloads the smaller result without uploading it. 3. The user draws redaction rectangles, previews the permanently flattened output, confirms the warning, downloads it, and clears all working data. SCREENS AND INFORMATION ARCHITECTURE Build these as coherent responsive views. Each screen must specify its primary action, secondary actions, visible status, validation feedback, empty state, loading or pending state, success confirmation, and recoverable failure state. 1. Job start: operation choices, file drop zone, supported limits, local-processing reassurance, encryption warning, and readable validation errors. 2. Page organizer: thumbnails, source document, order, rotation, selection, extract and delete controls, undo, zoomed preview, and processing state. 3. Compress and redact: preset or redaction tools, visible marks, irreversible-action explanation, before-and-after preview, and unsupported-feature warning. 4. Export: filename, page count, exact output size, download, start over, clear-working-data action, and failures that preserve the source selection. CORE CAPABILITIES 1. drag-and-drop PDF queue with page thumbnails 2. merge, reorder, rotate, extract, and delete pages 3. compression presets with before-and-after size 4. permanent rectangle redaction with explicit preview 5. download result and clear all local working data DETAILED BEHAVIOR AND BUSINESS RULES Treat these as server-enforced product requirements, not interface suggestions: 1. Keep source bytes and all intermediate documents in browser memory or isolated temporary storage and clear them on explicit reset, tab close where possible, or bounded expiry. 2. Parse PDFs with a maintained library inside a worker, cap file and page counts, reject unsupported encryption safely, and never execute embedded actions or scripts. 3. Implement redaction by removing or rasterizing covered content in the exported document; an annotation or opaque visual overlay never counts as redaction. 4. Build every result from an immutable operation list so undo is safe and failed processing cannot corrupt the original input. DATA MODEL AND LIFECYCLE Design a small relational schema centered on local DocumentJob, PageSelection, RedactionMark, ExportResult. Before implementing it, document: 1. Each table’s purpose, primary key, ownership or tenant boundary, timestamps, status fields, and important attributes. 2. Foreign keys, uniqueness constraints, check constraints, indexes needed by the named screens, and transaction boundaries for multi-record changes. 3. The allowed lifecycle or state transitions, who may trigger each transition, which transitions are terminal or reversible, and what audit history must remain immutable. 4. Archive, retention, and deletion behavior, including what happens to dependent records and external files. 5. Idempotency strategy for submissions, jobs, imports, notifications, webhooks, or retries where applicable. Use migrations rather than ad-hoc schema creation. Store time instants consistently and retain named timezone context whenever local schedules or dates matter. Never rely on a counter, disabled button, or client-side check to preserve a business invariant. USERS, AUTHENTICATION, AND PERMISSIONS Implement only the roles required by the stated audience. Make the ownership and visibility model explicit before coding. Enforce authorization in every server-side query and mutation, including search, exports, attachments, live updates, and guessed URLs—not merely by hiding controls. Use secure session defaults, protect state-changing requests, and provide an understandable signed-out, expired-session, and forbidden state. Seed distinct users when multiple roles are required so permissions can be demonstrated and tested. INTERACTION AND VISUAL DIRECTION The product should feel fast, calm, focused, and credible rather than like a generic admin template. Use a clear visual hierarchy, restrained color, readable typography, generous hit targets, and consistent placement for primary actions. Start with server-rendered HTML and progressively enhance only the interactions that benefit from it. The core workflow must remain understandable if enhancement fails. Render with React Server Components by default. Use Server Actions for authenticated form mutations and add Client Components only for interactions that genuinely require browser state, browser APIs, drag-and-drop, or live updates. The core workflow must remain understandable before client-side JavaScript finishes loading. Design mobile layouts intentionally instead of simply stacking desktop panels. Support keyboard navigation, visible focus, semantic landmarks, explicit labels, useful page titles, reduced-motion preferences, and screen-reader announcements for asynchronous results. Never use color alone to communicate state. Destructive actions require clear scope and confirmation; safe repeated actions should be idempotent. TECHNICAL DIRECTION Build this version with Next.js, the App Router, and TypeScript. Use Server Components by default, Server Actions for authenticated mutations, and Route Handlers for public APIs, OAuth callbacks, webhooks, feeds, uploads, and downloads. Use PostgreSQL through Drizzle ORM with versioned migrations and an isolated test database. Access S3-compatible object storage through a server-only adapter, and run slow or retryable work in a real job or workflow system instead of the request lifecycle. Keep domain rules in testable server-side modules instead of route handlers or UI components. Separate persistence, external providers, and background work behind small interfaces without building a framework. Prefer ordinary HTML forms and URLs for durable navigation; use optimistic interaction only when failure can be reconciled clearly. The product brief currently identifies Astro, Alpine, Browser API as capability context. Preserve any required native, browser-only, edge, storage, real-time, or background-processing capability through a narrow adapter appropriate to the selected framework. If the core workflow genuinely requires native or browser APIs, keep that runtime as the primary execution surface rather than simulating inaccessible capabilities or inventing an unnecessary web surface. Integrate with browser File API and PDF processing library and Web Workers. For every integration: - List required environment variables in an .env.example without real secrets. - Add a small adapter with timeouts, normalized errors, and a deterministic local fake or development path. - Verify inbound signatures and deduplicate provider events where supported. - Keep credentials server-side, encrypt long-lived provider tokens at rest, and redact secrets and sensitive payloads from logs. - Define retry, backoff, and idempotency behavior for any side effect that can be repeated. SECURITY AND PRIVACY Process documents locally by default, never fake redaction with overlays, and clearly warn when a file has signatures or unsupported encryption. Validate, normalize, and length-limit all untrusted input on the server. Escape rendered content by default, sanitize any intentionally accepted markup, rate-limit public or abuse-prone actions, and use private object storage plus short-lived authorized URLs for sensitive files. Collect the minimum personal data necessary for the named workflow. Document retention and deletion behavior. Add specific protections for the riskier surfaces in this app, such as uploads, redirects, outbound requests, email delivery, OAuth, webhooks, CSV import or export, and real-time connections. ACCEPTANCE SCENARIOS Automate these app-specific scenarios at the most appropriate level: 1. Given two supported PDFs, reorder and rotate produces a valid merged file in the exact previewed order while the originals remain unchanged. 2. Given an encrypted or malformed PDF, processing stops with a specific error and no partial output is offered as valid. 3. Given text underneath a confirmed redaction rectangle, extracting text from the exported PDF cannot recover the covered content. TESTING Add focused unit tests for state transitions, authorization predicates, normalization, date or money calculations, and other risky domain rules. Add integration tests for persistence constraints and each external adapter’s success, timeout, retry, and rejection paths. Add at least one browser-level test for every end-to-end journey above, including one small-screen viewport. Tests must use isolated data and run through a documented single command. OPERATIONS AND FAILURE RECOVERY Add structured server logs with request, job, or event correlation IDs but no secrets or unnecessarily sensitive data. Make failures actionable in both the interface and logs. Background work must expose pending, succeeded, failed, and retrying states where relevant; do not silently swallow errors. Include safe database migration and rollback guidance, seed data, backup and restore notes, external-data cleanup behavior, and a basic health or diagnostic path appropriate to the stack. DELIVERABLES Ship the working application, migrations, representative seed data, tests, .env.example, and a concise README. The README must cover prerequisites, local setup, environment variables, migrations, seed and test commands, deployment, integration setup, backup and restore, security decisions, and known limitations. Seed data should exercise the happy path plus at least one empty, failed, overdue, expired, archived, or permission-restricted state relevant to the product. DEFINITION OF DONE The app is complete when a fresh developer can follow the README, create and migrate the database, run the app, sign in as each relevant role, complete every named journey using real persisted data, refresh without losing state, recover from common failures, and use the core interface on phone and desktop. All acceptance scenarios pass, permission boundaries are covered by tests, and no core screen is left as a placeholder. NON-GOALS Do not add cloud storage, OCR, e-signatures, legal compliance claims, accounts, or collaborative review.
You are building a production-ready software product named “Paperknife”, a deliberately focused alternative to Adobe Acrobat Pro. Build a complete, usable vertical slice—not a landing page, static mockup, or disconnected collection of components. WORKING AGREEMENT Before writing implementation code, produce a short technical plan that names the routes or pages, server actions or endpoints, data tables, important state transitions, authorization boundaries, background jobs, and external adapters. Resolve contradictions in favor of the narrow audience and non-goals below. Prefer a small, legible architecture over speculative abstraction, but do not omit persistence, validation, error handling, or tests. PRODUCT BRIEF Primary user: one person handling ordinary non-sensitive PDF chores. Primary outcome: perform a small set of predictable PDF operations locally and download the result. Product principle: optimize the exact workflow below instead of copying the full breadth of Adobe Acrobat Pro. A first-time user should understand what to do from the interface itself, without a tour or documentation. END-TO-END USER JOURNEYS Implement all of these flows through the real interface and persistent data layer: 1. The user drops three PDFs, reviews their page thumbnails, reorders and rotates pages, removes an unwanted page, and downloads one merged document. 2. The user opens a large PDF, selects a compression preset, compares estimated and final size, and downloads the smaller result without uploading it. 3. The user draws redaction rectangles, previews the permanently flattened output, confirms the warning, downloads it, and clears all working data. SCREENS AND INFORMATION ARCHITECTURE Build these as coherent responsive views. Each screen must specify its primary action, secondary actions, visible status, validation feedback, empty state, loading or pending state, success confirmation, and recoverable failure state. 1. Job start: operation choices, file drop zone, supported limits, local-processing reassurance, encryption warning, and readable validation errors. 2. Page organizer: thumbnails, source document, order, rotation, selection, extract and delete controls, undo, zoomed preview, and processing state. 3. Compress and redact: preset or redaction tools, visible marks, irreversible-action explanation, before-and-after preview, and unsupported-feature warning. 4. Export: filename, page count, exact output size, download, start over, clear-working-data action, and failures that preserve the source selection. CORE CAPABILITIES 1. drag-and-drop PDF queue with page thumbnails 2. merge, reorder, rotate, extract, and delete pages 3. compression presets with before-and-after size 4. permanent rectangle redaction with explicit preview 5. download result and clear all local working data DETAILED BEHAVIOR AND BUSINESS RULES Treat these as server-enforced product requirements, not interface suggestions: 1. Keep source bytes and all intermediate documents in browser memory or isolated temporary storage and clear them on explicit reset, tab close where possible, or bounded expiry. 2. Parse PDFs with a maintained library inside a worker, cap file and page counts, reject unsupported encryption safely, and never execute embedded actions or scripts. 3. Implement redaction by removing or rasterizing covered content in the exported document; an annotation or opaque visual overlay never counts as redaction. 4. Build every result from an immutable operation list so undo is safe and failed processing cannot corrupt the original input. DATA MODEL AND LIFECYCLE Design a small relational schema centered on local DocumentJob, PageSelection, RedactionMark, ExportResult. Before implementing it, document: 1. Each table’s purpose, primary key, ownership or tenant boundary, timestamps, status fields, and important attributes. 2. Foreign keys, uniqueness constraints, check constraints, indexes needed by the named screens, and transaction boundaries for multi-record changes. 3. The allowed lifecycle or state transitions, who may trigger each transition, which transitions are terminal or reversible, and what audit history must remain immutable. 4. Archive, retention, and deletion behavior, including what happens to dependent records and external files. 5. Idempotency strategy for submissions, jobs, imports, notifications, webhooks, or retries where applicable. Use migrations rather than ad-hoc schema creation. Store time instants consistently and retain named timezone context whenever local schedules or dates matter. Never rely on a counter, disabled button, or client-side check to preserve a business invariant. USERS, AUTHENTICATION, AND PERMISSIONS Implement only the roles required by the stated audience. Make the ownership and visibility model explicit before coding. Enforce authorization in every server-side query and mutation, including search, exports, attachments, live updates, and guessed URLs—not merely by hiding controls. Use secure session defaults, protect state-changing requests, and provide an understandable signed-out, expired-session, and forbidden state. Seed distinct users when multiple roles are required so permissions can be demonstrated and tested. INTERACTION AND VISUAL DIRECTION The product should feel fast, calm, focused, and credible rather than like a generic admin template. Use a clear visual hierarchy, restrained color, readable typography, generous hit targets, and consistent placement for primary actions. Start with server-rendered HTML and progressively enhance only the interactions that benefit from it. The core workflow must remain understandable if enhancement fails. Start with server-rendered Blade views and ordinary forms. Use Livewire for focused server-driven interactions and Alpine.js only for small local interface state. The core workflow must remain understandable without relying on a client-side application shell. Design mobile layouts intentionally instead of simply stacking desktop panels. Support keyboard navigation, visible focus, semantic landmarks, explicit labels, useful page titles, reduced-motion preferences, and screen-reader announcements for asynchronous results. Never use color alone to communicate state. Destructive actions require clear scope and confirmation; safe repeated actions should be idempotent. TECHNICAL DIRECTION Build this version with Laravel, PHP, Blade, Livewire, and Alpine.js. Use controllers and Blade forms for durable navigation, Livewire for focused interactions, Form Requests for validation, Policies and Gates for authorization, and small application actions or services for domain transitions. Use Eloquent with migrations, database constraints, and transactions; Laravel Storage for private S3-compatible files; queued Jobs for retryable work; the Scheduler for recurring work; and Notifications or Mail for email. Keep domain rules in testable server-side modules instead of route handlers or UI components. Separate persistence, external providers, and background work behind small interfaces without building a framework. Prefer ordinary HTML forms and URLs for durable navigation; use optimistic interaction only when failure can be reconciled clearly. The product brief currently identifies Astro, Alpine, Browser API as capability context. Preserve any required native, browser-only, edge, storage, real-time, or background-processing capability through a narrow adapter appropriate to the selected framework. If the core workflow genuinely requires native or browser APIs, keep that runtime as the primary execution surface rather than simulating inaccessible capabilities or inventing an unnecessary web surface. Integrate with browser File API and PDF processing library and Web Workers. For every integration: - List required environment variables in an .env.example without real secrets. - Add a small adapter with timeouts, normalized errors, and a deterministic local fake or development path. - Verify inbound signatures and deduplicate provider events where supported. - Keep credentials server-side, encrypt long-lived provider tokens at rest, and redact secrets and sensitive payloads from logs. - Define retry, backoff, and idempotency behavior for any side effect that can be repeated. SECURITY AND PRIVACY Process documents locally by default, never fake redaction with overlays, and clearly warn when a file has signatures or unsupported encryption. Validate, normalize, and length-limit all untrusted input on the server. Escape rendered content by default, sanitize any intentionally accepted markup, rate-limit public or abuse-prone actions, and use private object storage plus short-lived authorized URLs for sensitive files. Collect the minimum personal data necessary for the named workflow. Document retention and deletion behavior. Add specific protections for the riskier surfaces in this app, such as uploads, redirects, outbound requests, email delivery, OAuth, webhooks, CSV import or export, and real-time connections. ACCEPTANCE SCENARIOS Automate these app-specific scenarios at the most appropriate level: 1. Given two supported PDFs, reorder and rotate produces a valid merged file in the exact previewed order while the originals remain unchanged. 2. Given an encrypted or malformed PDF, processing stops with a specific error and no partial output is offered as valid. 3. Given text underneath a confirmed redaction rectangle, extracting text from the exported PDF cannot recover the covered content. TESTING Add focused unit tests for state transitions, authorization predicates, normalization, date or money calculations, and other risky domain rules. Add integration tests for persistence constraints and each external adapter’s success, timeout, retry, and rejection paths. Add at least one browser-level test for every end-to-end journey above, including one small-screen viewport. Tests must use isolated data and run through a documented single command. OPERATIONS AND FAILURE RECOVERY Add structured server logs with request, job, or event correlation IDs but no secrets or unnecessarily sensitive data. Make failures actionable in both the interface and logs. Background work must expose pending, succeeded, failed, and retrying states where relevant; do not silently swallow errors. Include safe database migration and rollback guidance, seed data, backup and restore notes, external-data cleanup behavior, and a basic health or diagnostic path appropriate to the stack. DELIVERABLES Ship the working application, migrations, representative seed data, tests, .env.example, and a concise README. The README must cover prerequisites, local setup, environment variables, migrations, seed and test commands, deployment, integration setup, backup and restore, security decisions, and known limitations. Seed data should exercise the happy path plus at least one empty, failed, overdue, expired, archived, or permission-restricted state relevant to the product. DEFINITION OF DONE The app is complete when a fresh developer can follow the README, create and migrate the database, run the app, sign in as each relevant role, complete every named journey using real persisted data, refresh without losing state, recover from common failures, and use the core interface on phone and desktop. All acceptance scenarios pass, permission boundaries are covered by tests, and no core screen is left as a placeholder. NON-GOALS Do not add cloud storage, OCR, e-signatures, legal compliance claims, accounts, or collaborative review.
You are building a production-ready software product named “Paperknife”, a deliberately focused alternative to Adobe Acrobat Pro. Build a complete, usable vertical slice—not a landing page, static mockup, or disconnected collection of components. WORKING AGREEMENT Before writing implementation code, produce a short technical plan that names the routes or pages, server actions or endpoints, data tables, important state transitions, authorization boundaries, background jobs, and external adapters. Resolve contradictions in favor of the narrow audience and non-goals below. Prefer a small, legible architecture over speculative abstraction, but do not omit persistence, validation, error handling, or tests. PRODUCT BRIEF Primary user: one person handling ordinary non-sensitive PDF chores. Primary outcome: perform a small set of predictable PDF operations locally and download the result. Product principle: optimize the exact workflow below instead of copying the full breadth of Adobe Acrobat Pro. A first-time user should understand what to do from the interface itself, without a tour or documentation. END-TO-END USER JOURNEYS Implement all of these flows through the real interface and persistent data layer: 1. The user drops three PDFs, reviews their page thumbnails, reorders and rotates pages, removes an unwanted page, and downloads one merged document. 2. The user opens a large PDF, selects a compression preset, compares estimated and final size, and downloads the smaller result without uploading it. 3. The user draws redaction rectangles, previews the permanently flattened output, confirms the warning, downloads it, and clears all working data. SCREENS AND INFORMATION ARCHITECTURE Build these as coherent responsive views. Each screen must specify its primary action, secondary actions, visible status, validation feedback, empty state, loading or pending state, success confirmation, and recoverable failure state. 1. Job start: operation choices, file drop zone, supported limits, local-processing reassurance, encryption warning, and readable validation errors. 2. Page organizer: thumbnails, source document, order, rotation, selection, extract and delete controls, undo, zoomed preview, and processing state. 3. Compress and redact: preset or redaction tools, visible marks, irreversible-action explanation, before-and-after preview, and unsupported-feature warning. 4. Export: filename, page count, exact output size, download, start over, clear-working-data action, and failures that preserve the source selection. CORE CAPABILITIES 1. drag-and-drop PDF queue with page thumbnails 2. merge, reorder, rotate, extract, and delete pages 3. compression presets with before-and-after size 4. permanent rectangle redaction with explicit preview 5. download result and clear all local working data DETAILED BEHAVIOR AND BUSINESS RULES Treat these as server-enforced product requirements, not interface suggestions: 1. Keep source bytes and all intermediate documents in browser memory or isolated temporary storage and clear them on explicit reset, tab close where possible, or bounded expiry. 2. Parse PDFs with a maintained library inside a worker, cap file and page counts, reject unsupported encryption safely, and never execute embedded actions or scripts. 3. Implement redaction by removing or rasterizing covered content in the exported document; an annotation or opaque visual overlay never counts as redaction. 4. Build every result from an immutable operation list so undo is safe and failed processing cannot corrupt the original input. DATA MODEL AND LIFECYCLE Design a small relational schema centered on local DocumentJob, PageSelection, RedactionMark, ExportResult. Before implementing it, document: 1. Each table’s purpose, primary key, ownership or tenant boundary, timestamps, status fields, and important attributes. 2. Foreign keys, uniqueness constraints, check constraints, indexes needed by the named screens, and transaction boundaries for multi-record changes. 3. The allowed lifecycle or state transitions, who may trigger each transition, which transitions are terminal or reversible, and what audit history must remain immutable. 4. Archive, retention, and deletion behavior, including what happens to dependent records and external files. 5. Idempotency strategy for submissions, jobs, imports, notifications, webhooks, or retries where applicable. Use migrations rather than ad-hoc schema creation. Store time instants consistently and retain named timezone context whenever local schedules or dates matter. Never rely on a counter, disabled button, or client-side check to preserve a business invariant. USERS, AUTHENTICATION, AND PERMISSIONS Implement only the roles required by the stated audience. Make the ownership and visibility model explicit before coding. Enforce authorization in every server-side query and mutation, including search, exports, attachments, live updates, and guessed URLs—not merely by hiding controls. Use secure session defaults, protect state-changing requests, and provide an understandable signed-out, expired-session, and forbidden state. Seed distinct users when multiple roles are required so permissions can be demonstrated and tested. INTERACTION AND VISUAL DIRECTION The product should feel fast, calm, focused, and credible rather than like a generic admin template. Use a clear visual hierarchy, restrained color, readable typography, generous hit targets, and consistent placement for primary actions. Start with server-rendered HTML and progressively enhance only the interactions that benefit from it. The core workflow must remain understandable if enhancement fails. Start with server-rendered Rails views and ordinary forms. Use Turbo for navigation, submissions, and server-driven updates, then Stimulus only for small browser-side behavior. Do not turn the product into a client-side SPA, and keep the core workflow usable when enhancement fails. Design mobile layouts intentionally instead of simply stacking desktop panels. Support keyboard navigation, visible focus, semantic landmarks, explicit labels, useful page titles, reduced-motion preferences, and screen-reader announcements for asynchronous results. Never use color alone to communicate state. Destructive actions require clear scope and confirmation; safe repeated actions should be idempotent. TECHNICAL DIRECTION Build this version with Ruby on Rails and Hotwire: Turbo for navigation, form submissions, and server-driven updates, and Stimulus for small browser-side behavior. Use RESTful controllers with strong parameters and explicit authorization, with domain transitions in testable models or small application services. Use Active Record migrations plus database-level constraints and transactions; Active Storage with an S3-compatible service for private files; Active Job with a durable queue backend for retryable work; Action Mailer for email; and Action Cable only when live updates are required. Keep domain rules in testable server-side modules instead of route handlers or UI components. Separate persistence, external providers, and background work behind small interfaces without building a framework. Prefer ordinary HTML forms and URLs for durable navigation; use optimistic interaction only when failure can be reconciled clearly. The product brief currently identifies Astro, Alpine, Browser API as capability context. Preserve any required native, browser-only, edge, storage, real-time, or background-processing capability through a narrow adapter appropriate to the selected framework. If the core workflow genuinely requires native or browser APIs, keep that runtime as the primary execution surface rather than simulating inaccessible capabilities or inventing an unnecessary web surface. Integrate with browser File API and PDF processing library and Web Workers. For every integration: - List required environment variables in an .env.example without real secrets. - Add a small adapter with timeouts, normalized errors, and a deterministic local fake or development path. - Verify inbound signatures and deduplicate provider events where supported. - Keep credentials server-side, encrypt long-lived provider tokens at rest, and redact secrets and sensitive payloads from logs. - Define retry, backoff, and idempotency behavior for any side effect that can be repeated. SECURITY AND PRIVACY Process documents locally by default, never fake redaction with overlays, and clearly warn when a file has signatures or unsupported encryption. Validate, normalize, and length-limit all untrusted input on the server. Escape rendered content by default, sanitize any intentionally accepted markup, rate-limit public or abuse-prone actions, and use private object storage plus short-lived authorized URLs for sensitive files. Collect the minimum personal data necessary for the named workflow. Document retention and deletion behavior. Add specific protections for the riskier surfaces in this app, such as uploads, redirects, outbound requests, email delivery, OAuth, webhooks, CSV import or export, and real-time connections. ACCEPTANCE SCENARIOS Automate these app-specific scenarios at the most appropriate level: 1. Given two supported PDFs, reorder and rotate produces a valid merged file in the exact previewed order while the originals remain unchanged. 2. Given an encrypted or malformed PDF, processing stops with a specific error and no partial output is offered as valid. 3. Given text underneath a confirmed redaction rectangle, extracting text from the exported PDF cannot recover the covered content. TESTING Add focused unit tests for state transitions, authorization predicates, normalization, date or money calculations, and other risky domain rules. Add integration tests for persistence constraints and each external adapter’s success, timeout, retry, and rejection paths. Add at least one browser-level test for every end-to-end journey above, including one small-screen viewport. Tests must use isolated data and run through a documented single command. OPERATIONS AND FAILURE RECOVERY Add structured server logs with request, job, or event correlation IDs but no secrets or unnecessarily sensitive data. Make failures actionable in both the interface and logs. Background work must expose pending, succeeded, failed, and retrying states where relevant; do not silently swallow errors. Include safe database migration and rollback guidance, seed data, backup and restore notes, external-data cleanup behavior, and a basic health or diagnostic path appropriate to the stack. DELIVERABLES Ship the working application, migrations, representative seed data, tests, .env.example, and a concise README. The README must cover prerequisites, local setup, environment variables, migrations, seed and test commands, deployment, integration setup, backup and restore, security decisions, and known limitations. Seed data should exercise the happy path plus at least one empty, failed, overdue, expired, archived, or permission-restricted state relevant to the product. DEFINITION OF DONE The app is complete when a fresh developer can follow the README, create and migrate the database, run the app, sign in as each relevant role, complete every named journey using real persisted data, refresh without losing state, recover from common failures, and use the core interface on phone and desktop. All acceptance scenarios pass, permission boundaries are covered by tests, and no core screen is left as a placeholder. NON-GOALS Do not add cloud storage, OCR, e-signatures, legal compliance claims, accounts, or collaborative review.
Build just one piece
Not ready to replace all of Adobe Acrobat Pro? Fine. These are the peculiar sub-problems hiding inside it — the parts that are actually interesting to build. Each one is a standalone prompt, scoped to an evening, no strings attached to the full build.
Redaction that survives copy-paste forensicsA black rectangle is not redaction until the text underneath stops existing.
Build true redaction for a browser-based PDF tool. The user draws rectangles over sensitive content and confirms. The output document must not contain the covered content in any form: not as text objects under a black box, not in the content stream, not extractable by select-all and copy. Implement it by actually removing or rasterizing covered content, for each redacted region, either strip the intersecting text and image operators from the page's content stream, or rasterize the whole page to an image with the region blacked out and rebuild the page from that image. Rasterizing is cruder but safe; do it when precise stream surgery is uncertain. Show an explicit preview and an irreversibility warning before applying. Also scrub document metadata, title, author, and check for text hiding in annotations under the redaction area. Done when: extracting text from the exported PDF returns nothing from redacted regions, the visual output shows clean black rectangles exactly where drawn, and the original in-memory document remains untouched until export.
The undo stack made of operations, not snapshotsEvery edit is an entry in an immutable op list; the source bytes are never touched.
Build the operation architecture for a PDF manipulation tool. Never mutate the loaded PDF. Keep source bytes immutable in memory and represent every user action, reorder page 3 before page 1, rotate page 2 by 90, delete page 5, merge in document B, as an entry in an ordered operation list. The visible page organizer is a pure projection of sources plus operations; undo pops the last operation, redo re-pushes it, and neither touches any document bytes. Export replays the full operation list against the pristine sources to build the output document in one pass. This makes failure safe: if export crashes midway, the sources and the operation list are intact, and the user retries without data loss. Watch the index-shifting trap: operations reference stable page identities (source document plus original index), not current display positions, so undoing a delete doesn't misplace every later operation. Done when: any sequence of twenty mixed operations undoes back to the exact original state, a crashed export leaves the working state fully recoverable, and replaying the same operation list twice produces identical output files.
A thousand thumbnails without freezing the tabRender page previews in a worker, virtualize the grid, and keep drag-reorder at 60fps.
Build the page organizer for a client-side PDF tool: the user drops several PDFs and sees every page as a thumbnail in one reorderable grid. Parse and render in a Web Worker, the main thread only receives finished thumbnail bitmaps, so a 400-page document doesn't freeze the UI. Render lazily and in priority order: visible pages first, then nearby ones, with placeholder frames elsewhere, and virtualize the grid so DOM nodes stay bounded. Each thumbnail keeps its identity as source-document-plus-page-index, surviving reorders across source boundaries. Implement drag-to-reorder with a visible drop indicator, multi-select drag, and keyboard reordering for accessibility. Cap total pages and file sizes with readable errors, and reject encrypted PDFs at parse time with a specific message instead of a generic failure. Done when: dropping a 400-page PDF keeps the UI responsive while thumbnails stream in, dragging page 380 between pages from a different source document lands it exactly at the indicator, and an encrypted file fails with a named reason before any thumbnails render.
The compressor that admits when it can’t helpDownsample images, show real before-and-after sizes, and never bloat a file to “compress” it.
Build compression presets for a local-first PDF tool: light, balanced, and aggressive. PDF size usually lives in embedded images, so compression means finding image objects, downsampling ones whose resolution exceeds the preset's target DPI for their displayed size, and re-encoding at the preset's JPEG quality. Leave text, vectors, and fonts alone, that's where naive tools destroy documents. Be honest about outcomes. Compute the real output size before offering the download and show before and after side by side. Some PDFs, already-optimized ones, or pure text, won't shrink; if output is within a few percent of input or larger, say so and offer the original instead of shipping a worse file. Never upload anything: all processing happens in the browser, in a worker. Show per-preset estimates before running the full job by sampling a few pages. Done when: a scan-heavy PDF shrinks dramatically on aggressive while its text stays sharp, an already-small file yields an honest no-gain message rather than a larger output, and the page count and visible content are identical before and after.
Frequently asked questions
How long does it take to build your own Adobe Acrobat Pro?
A basic version — merge, split, rotate pdf pages — takes about 8 hours. Roughly 3 days gets you a solid v1 with compression presets, true redaction, thumbnails, local processing. Matching everything Adobe Acrobat Pro really does (ocr, e-signatures, form editing, a real pdf engine) is closer to 3 months+, which is exactly why you should scope down instead.
How much does Adobe Acrobat Pro cost if I keep subscribing?
Adobe Acrobat Pro runs $20–$30 per month on public paid plans, which is $240–$360 per year. A focused self-built replacement costs your build time plus close-to-zero hosting.
What stack should I use to build a Adobe Acrobat Pro alternative?
The build prompt on this page ships in four flavors: the AHA stack (Astro, HTMX, Alpine.js), Next.js, Laravel, and Ruby on Rails. The capability context for this product is Astro, Alpine, Browser API. Pick the stack you already know — the scope matters more than the framework.
What features does a minimal Adobe Acrobat Pro replacement need?
A useful v1 needs: drag-and-drop PDF queue with page thumbnails; merge, reorder, rotate, extract, and delete pages; compression presets with before-and-after size; permanent rectangle redaction with explicit preview; download result and clear all local working data. Everything else is scope creep until you personally miss it.
What should I deliberately not build?
Do not add cloud storage, OCR, e-signatures, legal compliance claims, accounts, or collaborative review.
Does this build also replace Smallpdf, iLovePDF, PDF Expert and DocHub?
Yes. Adobe Acrobat Pro, Smallpdf, iLovePDF, PDF Expert and DocHub all solve the same core job — perform a small set of predictable PDF operations locally and download the result. The scoped v1 on this page covers what most people use any of them for, so one focused build replaces whichever you currently pay for.