Protect PDF

New

Password-protect your PDF with encryption

PDF Tools

How to Use Protect PDF

  1. 1Upload a PDF
  2. 2Enter a password and confirm it
  3. 3Click Protect PDF
  4. 4Download the password-protected file

About Protect PDF

Protect PDF encrypts your document with a password using pdf-lib. Recipients need the password to open the file. No file is ever uploaded — everything runs in your browser.

Key Features of Protect PDF

  • Fast and accurate Protect Pdf processing
  • No installation required — works in browser
  • Free to use with no limitations
  • Privacy-focused — data never leaves your device
  • Mobile and desktop compatible
  • Instant results with live preview
  • No watermarks or content changes applied
  • No account or installation required

Supported Formats

Input Formats

PDF (unprotected)

Output Formats

PDF (RC4 128-bit password-protected)

Only user (open) password protection is applied. The PDF must not already be encrypted — unlock it first if needed.

Examples

Protect a contract before emailing

Add a password to a PDF contract so only the intended recipient can open it.

Input

Unprotected contract PDF

Output

Password-protected PDF — recipients need the password to open

Secure a financial report

Encrypt a sensitive financial PDF before uploading to a shared drive.

Input

Financial report PDF

Output

Encrypted PDF with password access control

Common Use Cases

  • Professional Protect Pdf tasks
  • Quick everyday calculations
  • Educational purposes and learning
  • Business and workplace productivity
  • Personal projects and hobbies
  • Securing academic thesis drafts during external review

Troubleshooting

Unexpected results

Solution

Double-check your input format and ensure all required fields are filled correctly.

Tool not working

Solution

Clear browser cache and refresh. Ensure JavaScript is enabled.

Trying to protect a PDF that is already password-protected

Solution

Unlock the PDF first with the Unlock PDF tool to remove the existing password, then add the new one.

Frequently Asked Questions

Is encryption done on a server?

No. pdf-lib encrypts your file entirely in your browser.

What if I forget the password?

There is no recovery. Store your password safely.

What encryption algorithm is used?

pdf-lib applies RC4 128-bit encryption, which is the standard user-password protection scheme supported by Adobe Acrobat, macOS Preview, and all major PDF viewers.

Can I restrict printing or copying while still allowing opening?

Currently only user (open) password protection is supported. Owner permission restrictions — such as disabling printing or text copying — are not separately configurable in this tool.

Will password protection work in all PDF readers?

Yes. Standard PDF user password encryption is a core part of the PDF specification and is supported by Adobe Acrobat, macOS Preview, browser PDF viewers, mobile apps, and all major PDF software.

Can I protect a PDF that already has a password?

No. The tool requires an unprotected PDF as input. Use the Unlock PDF tool to remove the existing password first, then apply the new password.

Can the password contain spaces or special characters?

Yes. Any printable character is allowed including spaces, punctuation, and symbols. Avoid extremely unusual Unicode characters for maximum compatibility across PDF readers.

What is the maximum password length?

Standard PDF encryption supports passwords up to 32 characters. For strong security, use at least 12 characters combining uppercase letters, lowercase letters, numbers, and symbols.