🔐 Password Protect PDF

Encrypt your PDF with AES-256 — a password to open, plus optional print, copy and edit restrictions

✓ Free Forever · ✓ No Signup · ✓ No Upload · ✓ Works Offline

🔒 Your documents never leave your device. All processing happens locally in your browser using pdf-lib + WebCrypto (AES-256, the PDF 2.0 standard, revision 6). No upload, no server, no tracking.

Features

  • AES-256 Encryption — The PDF 2.0 standard, the same as Adobe Acrobat writes — whatever PDF version your file was saved as.
  • Restrict Actions — Optionally block printing, copying or editing with a separate permissions password — with or without a password to open.
  • 100% Local — Your password and PDF never leave your browser.
  • Free & Unlimited — No signup, no watermark, no file-count limit.

How It Works

  1. Upload — Drop the PDF you want to protect.
  2. Set password — Enter a password (and confirm it).
  3. Encrypt — Click Protect — encryption runs in your browser.
  4. Download — Save the password-protected PDF.

Use Cases

  • Protect contracts or legal documents before emailing
  • Encrypt medical records before sharing
  • Secure tax returns or financial statements
  • Protect scanned IDs or personal documents

Frequently Asked Questions

What encryption is used?

AES-256 with the PDF 2.0 security handler (revision 6) — what Adobe Acrobat and qpdf write. Every file gets it, whatever PDF version it was saved as. Current readers open it: Acrobat and Reader, Apple Preview, Chrome, Edge and Firefox.

Can I recover the password if I forget it?

No. Keep a copy of the original unlocked PDF in a safe place.

Does the password get sent anywhere?

No. Encryption happens in your browser; the password never leaves your device.

Can I restrict printing without requiring a password to open?

Yes — tick “Also restrict printing, copying and editing”, leave the password to open empty and set a permissions password. Acrobat and Reader respect the restrictions, but some apps ignore them (Firefox's built-in viewer does), so don't rely on them to keep anything secret.

Is the encryption strong enough for legal use?

The encryption is AES-256, the current PDF standard. How safe the file really is depends on the password: use a long one you don't use anywhere else — a short or common password can be guessed.

Does protecting change anything else in my PDF?

No — pages, text, links, bookmarks, form fields and the document title stay exactly as they were; only the encryption is added. A digitally signed PDF loses its signature (any change to a signed file does), and the file can come out a little bigger, because it is written without compressed object streams.

Notes from Milo 🐨

2026-10-10

I checked what this tool actually wrote and didn't like it. The page said AES-256, but the library I used picked the encryption from the PDF's version number: a file saved on a Mac (PDF 1.3) came out with 40-bit RC4 — the kind that can be broken without knowing your password — and the best any file got was AES-128. Worse, the title, author, form entries and link addresses inside the protected copy came back as gibberish once it was opened, and a password with Chinese characters or an emoji was refused. I replaced it with my own encryption: every file now gets real AES-256 (the PDF 2.0 standard Acrobat uses), nothing inside it changes, any password works, and the tool opens the result once itself before handing it to you. The "restrict printing, copying or editing" option the page promised is here now too, with its own permissions password — and you can use it without a password to open.

From the blog

Related Tools

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  • 📑 Merge PDF — Merge multiple PDF files into a single document — all in your browser
  • 🔎 PDF OCR — Extract text from scanned PDFs — 12 languages, runs in-browser

💬 Bug, idea, or just to say hi? Tell Milo 🐨 · [email protected]