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Protect PDF with Password — Lock a PDF Online

To password-protect a PDF, select the file, type a password twice, and tap Add password. The PDF is encrypted in your browser with 128-bit encryption, so nobody can open it without the password, and neither the file nor the password is uploaded.

  • Free
  • No signup
  • Files never leave your device

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

How to password-protect a PDF

  1. 1Select or drop your PDF into the upload box.
  2. 2Type a password, then type it again to confirm.
  3. 3Tap Add password and download the protected PDF.
  4. 4Share the password separately from the file.
About Protect PDF: key facts and tips

Key facts

Documently Protect PDF adds an open password to a PDF, so any PDF reader asks for the password before showing a page. The file is encrypted with 128-bit RC4 encryption, the standard supported by virtually every PDF reader, including phone viewers and browsers. Printing and copying stay allowed for anyone who knows the password. The rewrite keeps images at their original quality: JPEG photos pass through unchanged and other images are stored losslessly. Passwords can use English letters, numbers, symbols and spaces, from 4 to 32 characters. There is no recovery option, so keep the password somewhere safe; forgotten passwords cannot be reset. Encryption runs inside the browser with Ghostscript compiled to WebAssembly, and neither the PDF nor the password is ever uploaded. The PDF engine, about 11 MB, downloads once on first use and then loads from the browser cache. To remove a password later, use Unlock PDF.

Emailing a salary slip, ITR or bank statement? Add a password first, then share the password separately, for example over a call or message. The PDF is locked on your device, and its pages and images stay exactly as they were.

Choosing a password

  • Longer is stronger: three or four unrelated words beat a short code.
  • Avoid your date of birth or mobile number. Banks often use those, and they are easy to guess.
  • Passwords are case-sensitive. The receiver must type it exactly.
  • Already locked? Remove the old password with Unlock PDF, then set a new one here.

Frequently asked questions

How do I put a password on a PDF for free?

Select your PDF here, type the password twice and tap Add password. Download the new file: it asks for the password whenever it is opened. No signup or app is needed.

Is my password or file sent anywhere?

No. The encryption runs in your browser, and neither the PDF nor the password leaves your device.

I forgot the password I set. Can it be recovered?

No. There is no recovery or reset, which is what makes the protection meaningful. Keep the original unprotected file, or note the password somewhere safe.

Will the protected PDF open on phones?

Yes. The 128-bit encryption used here is supported by standard PDF readers on Android, iPhone, Windows and Mac, as well as by Chrome and other browsers.

Last updated 31 October 2026. Questions or a spec that changed? hello@documently.in