PDFin: PDF Viewer, Sign, Stamp

Most PDF apps greet you with a subscription screen, and editing a file usually means uploading it to someone else's server. Contracts, medical records, IDs — do they really need to travel?

PDFin was built the other way around. There is no networking code in the app. Your documents never leave your device, and there are no subscriptions and no ads.

■ LIFETIME FREE FOR EARLY BIRDS Run the app for the first time on or before October 28, 2026, and that device gets every feature free for life. Eligibility is stored only on the device, so it cannot be restored after a reinstall or a device change (the free features remain available).

■ FREE FEATURES

• Fast viewer: opens a 47 MB document in 0.37 seconds, scrolls at 44.5 fps, and stays stable with a 452 MB file (our own measurements)
• Search with highlighting, page thumbnails
• Opens the body text of HWP, HWPX (Korean word-processor formats), DOCX, XLSX and TXT files
• Hand-drawn signatures and stamping
• Signature and seal library: import from photos, remove backgrounds, name each item — no limit on how many
• Three pen styles for handwriting
• OCR preview: recognize and copy the current page
• Dark mode

■ PRO FEATURES (one-time purchase)

• OCR the whole document and save it as a searchable PDF — processed on your device with Apple Vision / Google ML Kit, no internet needed
• Edit text: redraws your new text over the original (that is exactly how it works)
• Add text, insert photos, shapes, mosaic, color picker
• Create PDFs from text and images
• Page tools: merge, extract, rotate, delete, watermark, stamp, page numbers, password protect and remove
• Save HWP and other documents as PDF (body-text extraction)
• Extract text to .txt, flatten annotations, edit document info
• Vertical seal maker (Gothic sans-serif typeface)
• Batch save to PDF on macOS

■ WHY YOUR FILES STAY PUT This is not a promise — it is how the app is built. The app ships with no network entitlement at all. No accounts, no sign-in, no data collection. Purchases are handled by the App Store.

■ HONEST LIMITATIONS

• On mobile, documents over 120 MB cannot use text editing, search, OCR or save features (viewing and pen still work). Desktop handles up to 1 GB.
• Mosaic covers content visually only; the original text may remain inside the file. It is not permanent removal.
• Text selection and copying are not supported (use text extraction instead). No pinch zoom — use the buttons or Ctrl + wheel.
• HWP files show body text only: tables, images and formulas are excluded, and password-protected HWP files cannot be opened. Legacy doc/xls/ppt formats are not supported.

■ PRICING Installing and using the core features is free. Pro is a single $9.99 purchase — not a subscription, so there is nothing to pay next year or the year after. No ads; the free version shows one banner for our own apps, and Pro removes even that.

PDFin — THREE SEVEN TWELVE INC.