Protect PDF
Add a password with AES-256 encryption. The password never leaves your device.
Drop PDFs to protect
or select to choose from your device
Files are processed on this device. Nothing is uploaded.
How to use Protect PDF
- Add one or more PDFs.
- Enter a password twice. Optionally switch off printing, copying or editing.
- Select Protect PDF and download. Send the password to the recipient separately from the file.
How it works
The PDF is encrypted with AES-256, the strongest encryption defined in the PDF standard (PDF 2.0 / Acrobat X and later), using qpdf, a long-established open-source PDF library running here as WebAssembly. Without the password the contents cannot be read: this is real encryption, not a flag a viewer may ignore.
Because the file and the password are processed on your device, neither is sent to us or anyone else. That matters: uploading a confidential document and its password to a website defeats the purpose of protecting it.
The printing, copying and editing switches set the PDF’s permission flags. They are honoured by mainstream readers, but they are a request rather than a lock: anyone who can open the file can bypass them with the right software. The password is the real protection, and it is only as strong as you make it. Use a long passphrase; our password generator can make one.
Example
A scanned passport to send to a landlord: protect it with a passphrase of four random words, e-mail the PDF, and send the passphrase by text message.
Frequently asked questions
How strong is the protection?
AES-256 has no known practical attack. The weak point is the password: short or common passwords can be guessed by trying many candidates. Use at least 12 characters or several random words.
What if I forget the password?
The file cannot be opened. There is no recovery and we cannot help, because we never see the file or the password. Keep the original or store the password in a password manager.
Is the password sent to your server?
No. Encryption happens in your browser. You can load the page, disconnect from the internet and it still works.
Will the protected PDF open everywhere?
In any reader released in roughly the last 15 years, including Adobe Reader, Chrome, Edge, Firefox, Preview on Mac and phone PDF viewers. Very old software may not support AES-256.
Can I stop people printing or copying?
You can switch those permissions off, and normal readers will obey. Treat this as a deterrent: determined users can bypass permission flags once they can open the file.
Limitations
- A forgotten password cannot be recovered by anyone.
- Permission restrictions (print, copy, edit) are advisory and can be bypassed with other software.
- A PDF that already needs a password must be unlocked first.
- File names and file size are not hidden by encryption.
Last reviewed November 9, 2026. How we build and test tools.