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Protect PDF

Add an open password to a PDF with AES-256 encryption.

Drop your PDF here

Choose an unprotected PDF and add an open password.

One PDF · Up to 50 MB · 100 pages

Changing PDF encryption may invalidate existing digital signatures.

Protect & Unlock guide

How to use Protect PDF

Require readers to enter a password before they can open a PDF document.

Three simple steps

  1. Choose an unprotected PDF.
  2. Enter and confirm a strong, unique password.
  3. Protect the document and download the encrypted PDF.

Password protection

  • The downloaded PDF uses AES-256 encryption.
  • Anyone opening the file will need the password.
  • Store the password safely because forgotten passwords cannot be recovered here.

Frequently asked questions

Can smallpdf.app recover a forgotten password?

No. Keep a secure copy of the password.

Can protection affect digital signatures?

Rewriting PDF encryption may invalidate existing certificate-backed signatures.

What encryption does the result use?

The protected PDF uses AES-256 encryption and requires the open password.