Protect PDF
This free Protect PDF tool encrypts a PDF with a password using AES-256, so it can only be opened by someone who knows the password. Drop in your file, set a password (or generate a strong one), and download the protected copy — the PDF is encrypted on your device and never uploaded.
How to use Protect PDF
- 1 Drop a PDF onto the box or click to browse for one.
- 2 Type a password and confirm it, or click Generate password and pick a length to create a strong one.
- 3 Optionally tick Show to check what you typed.
- 4 Click Protect PDF to encrypt it with AES-256.
- 5 Download the protected file — remember the password, because it is required to open the PDF and cannot be recovered.
Frequently asked questions
Is my PDF uploaded to a server to encrypt it?
No. Encryption happens entirely in your browser on your device, so the PDF and its password never leave your computer. That makes it safe for sensitive or confidential documents.
What encryption does it use?
The PDF is encrypted with AES-256, a strong standard supported by modern PDF readers. Anyone opening the file will be prompted for the password you set.
What happens if I forget the password?
There is no way to recover it. The password is never stored or sent anywhere, so keep a copy somewhere safe before you close the tool.
Are there characters I can't use in the password?
Commas and equals signs are not allowed because of how the PDF encryption options are written. The built-in password generator automatically avoids them.