Password Protect PDF

Lock a PDF with a password — encrypt PDFs in your browser.

Add a password to a PDF so only people who know it can open the file — the simplest way to secure contracts, invoices, bank statements and private documents before you share them. Choose a password (with a live strength meter and confirm field) and the PDF is encrypted with strong AES encryption right in your browser via @cantoo/pdf-lib. The file and password never leave your device, and there's no sign-up or watermark.

Password Protect PDF features

How to use Password Protect PDF

  1. Upload your PDF

    Drop the PDF you want to secure into this free online protect PDF tool or click to select it — it stays on your device and is never uploaded anywhere.

  2. Choose a strong password

    Type the password you want to lock the file with. A live strength meter shows whether it's weak, fair, good or strong as you type.

  3. Confirm it

    Re-type the same password in the confirm field — this catches typos before the file is encrypted, so you don't lock yourself out by mistake.

  4. Protect the PDF

    Click Protect PDF and the document is encrypted right in your browser with a password that will be required every time someone opens the file.

  5. Download the secured PDF

    Click Download protected PDF to save the encrypted copy — it replaces nothing, so your original file stays untouched.

  6. Share it safely

    Send the protected PDF by email or cloud link as usual, then share the password separately (a text or call works well) so only the intended reader can open it.

Frequently asked questions

How do I password protect a PDF for free?

Upload your PDF, set and confirm a password, then click Protect PDF and download the encrypted file. There's no sign-up, no watermark and no limit — and it all runs in your browser.

What encryption is used?

The PDF is encrypted with the standard AES algorithm supported by all major PDF readers, applied entirely on your device via @cantoo/pdf-lib.

Is my file or password uploaded?

No. Both the PDF and the password stay in your browser — encryption happens locally. Nothing is uploaded, logged or stored on any server.

What happens if I forget the password?

There's no recovery. The whole point of encryption is that the file can't be opened without the password, so store it somewhere safe like a password manager.

Can the recipient open it on any device?

Yes. The protected PDF opens in Adobe Acrobat, Preview, Chrome, Edge and every standard PDF viewer — the reader simply prompts for the password first.

Does this work on mobile?

Yes. Because everything runs in your browser, you can password-protect a PDF on a phone, tablet or desktop with no app to install.

Can I remove the password later?

Yes. If you have the password, use the Unlock PDF tool to strip the protection and save an unprotected copy — so locking a file here is fully reversible as long as you remember the password.

Is password-protecting a PDF free and without a watermark?

Yes — it's completely free with no sign-up and no watermark added to your file. The encryption is applied in your browser, so the PDF and password never leave your device.

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