How ProMaxPDF works
There is no upload API for your documents. A tool page on promaxpdf.pro reads a File as an ArrayBuffer, runs pdf-lib / PDF.js / Tesseract in this tab (often in a Worker), and triggers a download. Open DevTools → Network while merging: you should not see the PDF posted anywhere.
Libraries
- pdf-lib (Cantoo fork) — merge, split, encrypt AES-256, forms, page ops
- PDF.js — render and extract text
- Tesseract.js — OCR as a searchable scan (image stays, invisible text underneath)
- SheetJS, Mammoth, jsPDF — Office / HTML conversions (fidelity is best-effort)
- Web Crypto — hashes and optional P2P payload encryption
- PeerJS / WebRTC — P2P share and whiteboard (no app server of our own)
What does leave the device
- P2P / whiteboard: connection metadata through a public WebRTC broker. File bytes and strokes travel peer-to-peer.
- Speech recognition: whatever your browser vendor already does.
Limits
Phones cap around 50 MB / 300 DPI. Desktops around 150 MB / 600 DPI. Long jobs batch pages and release canvases so the tab is less likely to die.