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Protect PDF

Lock a PDF with a password before you email or share it. Everything happens on your device.

Share it separately from the file, for example by phone. It can't be recovered if you forget it.

Restrict printing, copying or editing (optional)

Needed to change the permissions later. Leave it empty and a random one is used; the open password can still remove all protection with Unlock PDF.

Runs in your browser: your file and password are never uploaded.

How to password-protect a PDF

  1. Choose the PDF (up to 100 MB).
  2. Type a password, then type it again to make sure there's no typo. Tick Show passwords to check it.
  3. Optionally open Restrict printing, copying or editing, and set a separate permissions password.
  4. Press Protect PDF and download the copy ending in -protected.pdf. Your original file is not changed.

How the encryption works

The PDF is encrypted with AES-256, the strongest method in the PDF standard (PDF 2.0, security handler revision 6). Every page, picture and piece of text is scrambled, and only the password can turn it back. Current versions of Adobe Acrobat and Reader, Chrome, Edge, Firefox, macOS Preview and phone PDF apps open it after asking for the password; very old readers (Adobe Reader 9 and earlier) can't open it at all.

Before the download is offered, the tool opens the protected copy again with your password, so you never get a file your password doesn't open. If the PDF already has a password, you're asked for it first, and the new password replaces the old one.

Two kinds of password

  • Open password: needed to see the PDF at all. This is the one you share with the reader.
  • Permissions password: lets its holder change the printing, copying and editing limits. If you leave it empty, a random one is set; you can still remove all protection later with Unlock PDF and the open password.

Example

A salary slip sent to an accountant: protect it with a passphrase such as blue-mango-river-42, untick Allow editing, and send the password by phone or SMS rather than in the same email as the file. The accountant can open and print it, but their PDF app won't let them change it.

Tips for a strong password

  • Use three or four unrelated words with a number: long passphrases are harder to guess than short, complicated ones. Check one with the password strength checker.
  • Don't reuse a password from your email or bank.
  • Passwords can be up to 127 bytes: 127 English letters, or fewer in Hindi, Tamil and other scripts that need more bytes per letter.

Uses qpdf 12.2.0 (Apache License 2.0), compiled to WebAssembly with zlib and libjpeg-turbo and served from this site, so it runs in your browser. This software is based in part on the work of the Independent JPEG Group. Licence notices.

Frequently asked questions

How do I put a password on a PDF?

Choose the PDF, type the password twice and press Protect PDF, then download the protected copy. From then on, every PDF reader asks for that password before it shows the file.

Is my PDF or password uploaded?

No. The encryption runs in your browser with qpdf compiled to WebAssembly. The file and the password stay on your device, and nothing is stored.

Can you recover a forgotten password?

No. We never see or keep it, and AES-256 can't be undone without it. Keep the password somewhere safe, or keep an unprotected copy in a private place.

Can I stop people printing or copying from my PDF?

Yes: open Restrict printing, copying or editing and untick what you want to block. Readers such as Adobe Acrobat and Chrome respect these limits, but they are not encryption, so some apps ignore them. The open password is the real protection.

How do I remove the password later?

Use Unlock PDF with the same password. It saves a copy that opens without one.

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