Protect PDF
Add a password to a PDF to restrict who can open it.
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PDF · up to 100 MB
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How it works
Enter a password and a new AES-encrypted copy of the PDF is produced. Anyone opening the file will be prompted for the password. Encryption happens locally in your browser.
Common use cases
- Encrypting a payslip or a tax return before storing it in a shared cloud folder.
- Password-protecting a contract before sending it by email so the recipient's inbox breach doesn't leak it.
- Adding a layer of protection to a signed document that must not be modified in transit.
Privacy
This tool runs entirely in your browser. Your PDF is never uploaded to our servers — the file stays on your device from start to finish.
Combined workflows
Most people pair Protect PDF with Unlock PDF, Sign PDF and Watermark PDF.
FAQ
What encryption is used?
AES via the @cantoo/pdf-lib library — the modern PDF encryption standard, respected by every PDF viewer including Adobe Reader, Preview, and browsers.
What happens if I lose the password?
The file cannot be recovered. There is no backdoor, no reset, no support ticket. Store the password somewhere safe (a password manager) before you close the tab.