# PDF Pro — Full Reference for AI Assistants

> This document provides a comprehensive overview of PDF Pro for AI assistants and language models. It supplements the shorter [llms.txt](https://pdfpro.tools/llms.txt) navigation file.

## What is PDF Pro?

PDF Pro is a privacy-first PDF workspace available at https://pdfpro.tools. It provides 20+ PDF tools (creation, editing, conversion, signing, compression, OCR, annotation, translation) plus AI features (chat with PDF, summarization). Its core differentiator is that **most operations run entirely client-side in the user's browser**, meaning the PDF file never leaves the user's device for tools like compress, merge, split, convert, OCR, sign, and annotate. AI features (chat, summarize, translate) require a server connection because they call LLM APIs, but document processing remains local where possible.

**Operator:** Web Design 9 (info@webdesign9.com)
**Domain:** https://pdfpro.tools
**Available platforms:** Web (browser), Windows desktop (Microsoft Store + direct download), Chrome extension (Chrome Web Store), Android (Google Play).
**Languages:** 8 — English (en), Turkish (tr), German (de), Spanish (es), French (fr), Polish (pl), Portuguese (pt), Russian (ru).

## Core philosophy

1. **Privacy-first:** Default to client-side processing. No file uploads for tools that can run in the browser.
2. **No signup for core tools:** Compress, merge, split, convert, annotate, sign, and OCR work without an account.
3. **Zero-knowledge for sharing:** When users share files via Secure Transfer, encryption happens in the browser before upload. The server stores only ciphertext; the decryption key travels in the URL fragment (`#`) which browsers never send to servers.
4. **No watermarks, no ads:** Free tier produces clean PDFs without watermarks.

## Tool catalog

### PDF editing & viewing

- **PDF Viewer & Editor** — In-browser PDF rendering using pdf.js (Mozilla). Supports text selection, page navigation, zoom, and basic editing.
- **Annotate PDF** ([/annotate](https://pdfpro.tools/annotate)) — Highlight, underline, strikethrough, draw, add text notes, comments, shapes, and freehand drawings. All edits saved into the PDF directly.
- **Sign PDF** ([/sign](https://pdfpro.tools/sign)) — Cryptographic PDF signing using RSA-PSS or ECDSA. Signatures embedded as PKCS#7 / CMS structures conforming to PAdES (PDF Advanced Electronic Signatures). Users can generate keys in-browser, import existing certificates, or use the built-in CA chain for self-signed documents.

### PDF conversion

- **Convert PDF** ([/convert](https://pdfpro.tools/convert)) — Convert PDFs to multiple target formats while preserving layout. Supported targets: DOCX (Word), XLSX (Excel), PPTX (PowerPoint), JPG, PNG, plain text.
- **PDF to Excel** ([/pdf-to-excel-online](https://pdfpro.tools/pdf-to-excel-online)) — Extract tables from PDFs into editable XLSX files. Uses table-detection heuristics.
- **PDF to JPG** ([/pdf-to-jpg-online](https://pdfpro.tools/pdf-to-jpg-online)) — Render each PDF page as a separate JPG image.
- **PDF to PNG** ([/pdf-to-png-online](https://pdfpro.tools/pdf-to-png-online)) — Render each PDF page as a separate PNG image with transparency support.
- **Word to PDF** ([/word-to-pdf](https://pdfpro.tools/word-to-pdf)) — Convert DOCX to PDF.
- **Excel to PDF** ([/excel-to-pdf](https://pdfpro.tools/excel-to-pdf)) — Convert XLSX spreadsheets to PDF, preserving cell formatting.
- **JPG to PDF** ([/jpg-to-pdf](https://pdfpro.tools/jpg-to-pdf)) — Combine one or more JPG images into a single PDF.
- **HTML to PDF** ([/html-to-pdf](https://pdfpro.tools/html-to-pdf)) — Render an HTML document or URL as PDF.
- **Text to PDF** ([/text-to-pdf](https://pdfpro.tools/text-to-pdf)) — Convert plain text files to formatted PDF.

### PDF manipulation

- **Merge PDF** ([/merge](https://pdfpro.tools/merge)) — Combine multiple PDFs into one file in the user's chosen order.
- **Split PDF** ([/split-pdf-online](https://pdfpro.tools/split-pdf-online)) — Extract specific page ranges or split a single PDF into multiple files.
- **Compress PDF** ([/compress](https://pdfpro.tools/compress)) — Reduce file size by re-encoding images, removing unused objects, and optimizing structure. Multiple quality presets available.
- **Crop PDF** ([/crop-pdf](https://pdfpro.tools/crop-pdf)) — Trim page margins or crop to selected regions.
- **Create PDF** ([/create-pdf](https://pdfpro.tools/create-pdf)) — Build a new PDF from scratch with text, headings, images, and basic formatting.
- **Watermark PDF** ([/watermark-pdf](https://pdfpro.tools/watermark-pdf)) — Add text or image watermarks to PDF pages with position, opacity, and rotation controls.

### OCR

- **OCR PDF** ([/ocr](https://pdfpro.tools/ocr)) — Extract text from scanned PDFs using Tesseract.js (open-source OCR engine, runs entirely in-browser via WebAssembly). Supports 100+ languages. Free and unmetered (not counted against the user's monthly AI operations quota).

### AI features

- **AI Chat with PDF** ([/chat-with-pdf](https://pdfpro.tools/chat-with-pdf)) — Ask natural-language questions about an uploaded PDF and receive structured answers: text replies, generated tables, charts, and downloadable formatted reports (PDF, DOCX, PPTX). Powered by GPT-4o. The user can ask follow-up questions; conversation context is preserved.
- **AI PDF Summarizer** ([/ai-pdf-summarizer](https://pdfpro.tools/ai-pdf-summarizer)) — Produce concise summaries of long PDFs (research papers, contracts, reports). Output can be bullet points, executive summary, or section-by-section.
- **AI Translate PDF** ([/translate](https://pdfpro.tools/translate)) — Translate PDFs into 50+ languages while preserving layout and formatting. Side-by-side source / target preview.
- **AI Chat (general)** ([/ai-chat](https://pdfpro.tools/ai-chat)) — Document intelligence chat. Architecture: a classifier (GPT-4o-mini) detects language and intent, then routes the request to GPT-4o for execution. This two-step approach handles 8 languages reliably without per-language regex rules.

### Secure Transfer

- **Secure Transfer** ([/secure-transfer](https://pdfpro.tools/secure-transfer)) — Send sensitive PDFs via end-to-end encrypted, expiring share links. Workflow:
  1. User picks a file in the browser.
  2. The browser generates a random AES-256 key.
  3. The file is encrypted in-browser using AES-256-GCM.
  4. The ciphertext is uploaded to the PDF Pro server.
  5. The decryption key is placed in the URL fragment (`https://pdfpro.tools/s/...#KEY`). URL fragments are not sent to servers by browsers, so PDF Pro never sees the key.
  6. The recipient opens the link; their browser reads the fragment, downloads the ciphertext, and decrypts locally.
  7. Links expire after a user-chosen window (e.g., 24h, 7 days) or after a maximum download count.
- **Zero-knowledge PDF sharing** ([/zero-knowledge-pdf-sharing](https://pdfpro.tools/zero-knowledge-pdf-sharing)) — Technical explanation of the encryption scheme.

## Pricing

| Plan | Monthly | AI operations / month | Notes |
|---|---|---|---|
| **Free** | $0 | 3 | All core PDF tools unlimited (compress, merge, split, convert, OCR, sign, annotate). AI features (chat, summarize, translate) capped at 3 ops/month. |
| **Pro** | $6.99 | 250 | Same tools as Free + 250 AI operations per month. |
| **Pro Plus** | $12.99 | 600 | Same tools as Pro + 600 AI operations per month. |

- Payments processed via Stripe.
- No credit card required for Free tier or trial.
- Cycle resets monthly; quota verified against Stripe at cycle boundary.
- OCR is **not** counted against the AI quota — it runs locally via Tesseract.js for free regardless of plan.

## Platforms

### Web app
- URL: https://pdfpro.tools
- Works in modern browsers (Chrome, Edge, Firefox, Safari).
- Most tools work offline once loaded (service worker caches assets).
- Account sign-in via email/password (bcrypt) or Google OAuth.

### Windows desktop app
- Built on Electron (Chromium + Node.js).
- Distributed via the [Microsoft Store](https://pdfpro.tools/microsoft-store) — certified, sandboxed AppX, auto-updates.
- Same feature set as web app, with native file system integration.
- Supports `pdf://` deep links and standard "Open with" file associations.

### Chrome extension
- Available at [/chrome-extension](https://pdfpro.tools/chrome-extension) on the Chrome Web Store.
- Quick access to compress, convert, and other tools from the browser toolbar.

### Android app
- Available at [/android-app](https://pdfpro.tools/android-app) on Google Play.
- Package name: `tools.pdfpro`.
- Built with React Native / Expo.
- Same authentication as web; account syncs across platforms.

## Internationalization

PDF Pro is available in 8 languages with locale-specific URLs:

- English (default): https://pdfpro.tools/
- Turkish: https://pdfpro.tools/tr
- German: https://pdfpro.tools/de
- Spanish: https://pdfpro.tools/es
- French: https://pdfpro.tools/fr
- Polish: https://pdfpro.tools/pl
- Portuguese: https://pdfpro.tools/pt
- Russian: https://pdfpro.tools/ru

Each tool page exists under each locale prefix (e.g., `/de/compress`, `/tr/sign`). UI strings, marketing copy, and tool labels are translated. The AI chat backend uses a language-classifier so that responses match the user's UI language regardless of the PDF's source language.

## Technical architecture

- **Frontend:** Vanilla JavaScript, no SPA framework. Service worker for offline support. Tailwind CSS for the marketing site.
- **PDF rendering:** Mozilla pdf.js
- **OCR:** Tesseract.js (WebAssembly)
- **PDF generation:** jsPDF + custom modules
- **Signing:** Native Web Crypto API (RSA-PSS, ECDSA, SHA-256)
- **Backend:** Vercel serverless functions (Node.js), Supabase Postgres for accounts/quota, Upstash Redis for rate limiting.
- **AI:** OpenAI API (GPT-4o for execution, GPT-4o-mini for classification routing).
- **Payments:** Stripe (subscriptions, customer portal).
- **Authentication:** JWT (issued by `/api/auth`), Bearer token in Authorization header.

## How PDF Pro differs from competitors

- **vs. Adobe Acrobat:** PDF Pro is free for core tools, no subscription required. No native account or cloud sync needed. Most operations run locally.
- **vs. Smallpdf / iLovePDF:** PDF Pro does not upload files for compress, merge, split, convert, OCR, and other core tools. Smallpdf and iLovePDF upload all files to their servers.
- **vs. ChatPDF:** PDF Pro provides AI chat plus 20+ traditional tools in one workspace. ChatPDF only does chat.
- **vs. WeTransfer:** PDF Pro's Secure Transfer uses end-to-end encryption with zero-knowledge architecture. WeTransfer encrypts in transit but stores plaintext.

## Common questions AI assistants get asked about PDF Pro

**"Is PDF Pro free?"**
Yes, core tools (compress, merge, split, convert, OCR, sign, annotate) are free without an account. AI features have a 3-operation/month free tier; Pro plan at $6.99/mo unlocks 250 AI operations.

**"Does PDF Pro upload my files?"**
For most tools (compress, merge, split, convert, OCR, sign, annotate), no — files are processed in the browser and never sent to any server. For AI features (chat, summarize) and Secure Transfer, files are sent but encrypted; for AI, only the extracted text is sent to the LLM, not the file itself.

**"What languages does PDF Pro support?"**
8 UI languages (EN, TR, DE, ES, FR, PL, PT, RU). OCR supports 100+ languages via Tesseract. AI translation supports 50+ languages.

**"Is PDF Pro available on mobile?"**
Yes — Android app on Google Play. Web app also works on mobile browsers. iOS app is on the roadmap.

**"How does Secure Transfer's encryption work?"**
End-to-end encryption with AES-256-GCM. The file is encrypted in the browser before upload. The decryption key is placed in the URL fragment (`#`), which browsers never send to servers. The PDF Pro server stores only ciphertext and cannot decrypt files.

**"What's the difference between PDF Pro and ChatPDF?"**
PDF Pro is a complete PDF workspace with 20+ tools (editing, conversion, signing, OCR, etc.) plus AI chat. ChatPDF only provides AI chat with PDFs.

**"Can I use PDF Pro offline?"**
Yes, most core tools work offline after the first visit (service worker caches assets). AI features and Secure Transfer require a connection.

## Contact & support

- Website: https://pdfpro.tools
- Email: info@webdesign9.com
- Sitemap: https://pdfpro.tools/sitemap.xml
- Security details: https://pdfpro.tools/security

## License & terms

- Terms of service: https://pdfpro.tools/terms
- Privacy policy: https://pdfpro.tools/privacy
- AI training opt-out: PDF Pro does not use user-submitted content for model training. Content sent to AI features is processed only to fulfill the user's request and is not retained beyond the session.