About the Protect PDF
Protecting a PDF adds a password so the file can only be opened by someone who knows it. This tool encrypts your PDF with real AES-256 encryption, the same strength used by banking and government systems, directly in your browser. Choose a password, confirm it, and download a copy of the PDF that asks for that password before it will open in any PDF reader.
How to use the Protect PDF
- Choose the PDF you want to protect.
- Type a password and confirm it.
- Click Protect PDF.
- Download the password-protected copy.
Features
- Real AES-256 encryption, not just a filename trick
- Only opens with the password you set
- Works with any PDF reader that supports standard PDF encryption
- Processed entirely in your browser - the PDF is never uploaded
- No watermark, no page limit
How strong is the encryption?
The PDF is encrypted with AES-256, the same algorithm widely used to protect sensitive data, via the open-source QPDF library running inside your browser as WebAssembly. Without the password, the file's contents cannot be read by a PDF viewer.
What if I forget the password?
There is no way to recover a forgotten password from an AES-256 protected PDF, by design - that is what makes the protection effective. Keep a copy of the password somewhere safe, such as a password manager, and keep the original unprotected file until you are sure you will remember it.
Frequently asked questions
Does this upload my PDF anywhere?
No. The file is encrypted entirely in your browser with JavaScript using a WebAssembly build of QPDF, and never leaves your device.
What encryption does this use?
AES-256, the modern standard for PDF encryption, applied with the open-source QPDF library compiled to run in the browser.
Can I remove the password later?
Yes. Use the Unlock PDF tool with the password you set to produce a copy without it.
Will the password-protected PDF open in any PDF reader?
Yes. It uses the standard PDF encryption format supported by Adobe Acrobat, browsers and most other PDF readers, which will prompt for the password before opening it.