PDF Tool

Password Protect PDF

Password-protect your PDF so only authorised recipients can open it. Note: browser-based PDF encryption is not yet supported — see the FAQ for desktop alternatives.

🔒 Zero uploads — stays on your device 🔑 Password set locally ⚡ Instant processing

Frequently Asked Questions

Is browser-based PDF encryption supported?

Currently, our browser-only engine (pdf-lib v1) does not implement the AES-128/RC4 stream encryption required by the PDF standard. Attempting to protect a PDF will show a clear error message with desktop alternatives. Full browser-based encryption is planned for a future release using a WASM-based crypto library.

What desktop tools can I use to password-protect a PDF?

LibreOffice Writer (File → Export as PDF → Security tab → Set open password), Adobe Acrobat, PDFtk (free command-line: pdftk in.pdf output out.pdf user_pw PASSWORD), or Preview on macOS (File → Export as PDF → Show Details → Security Options).

Is the Unlock PDF tool affected?

No — unlocking (removing encryption from) a PDF works correctly, since pdf-lib supports decrypting an already-encrypted PDF when you supply the correct password.