# Password protect a PDF

> Lock a PDF with a password using AES-256 in your browser, and optionally block printing, copying or editing. The file and password never leave your device.

URL: https://tools.cuelark.com/protect-pdf
Publisher: Cuelark Team (https://cuelark.com)
Updated: 2026-11-10
Price: free, no sign-up
Privacy: runs in the browser; files are not uploaded

Set a password and the PDF is encrypted with AES-256, the strongest standard PDF encryption. It runs in this tab with qpdf compiled to WebAssembly, so neither the document nor the password is sent anywhere.

## How to use it

1. Drop the PDF.
2. Type the password twice. Optionally set a separate owner password and turn printing, copying or editing off.
3. Press Protect PDF and download. Keep the password safe: there is no way to recover it.

## Details

- **Encryption:** AES-256 (PDF 2.0 / Acrobat X and later). Opens in Adobe Reader, Chrome, Edge, Firefox, macOS Preview and phone viewers
- **Restrictions:** Printing, copying text and editing can be turned off; they apply in readers that respect PDF permissions
- **Engine:** qpdf (Apache-2.0) compiled to WebAssembly, about 1.3 MB, downloaded only on this page

## Questions

### Are my files uploaded?

No. The page loads its code once, then reads and processes your files inside the browser tab. Nothing is sent to a server; you can confirm it in your browser's network panel while a file is processed.

### What is the owner password?

It unlocks the restrictions (printing, copying, editing). The open password lets people read the file. If you leave the owner password empty, the open password is used for both.

### How strong is the protection?

AES-256 with a long password cannot be broken by guessing in practice. A short or common password can be. Use at least 10 characters, or a passphrase of several words.

### I forgot the password. Can you recover it?

No. The password never leaves your device, and nobody, including us, can open the file without it.

### Are the print and copy restrictions secure?

They are honoured by mainstream readers but are not strong security: some tools ignore them. The open password is the real protection.

## Related tools

- [Sign a PDF](https://tools.cuelark.com/sign-pdf)
- [Add a watermark to a PDF](https://tools.cuelark.com/watermark-pdf)
- [Compress PDF to a size you choose](https://tools.cuelark.com/compress-pdf)
- [Merge PDF](https://tools.cuelark.com/merge-pdf)