Protect PDF
Password-protect a PDF with AES-256 encryption. The password never leaves your browser — neither does the file. Free, no signup.
Upload PDF
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Files are processed locally and never uploaded
Quick Answer
Add a password that is required to open the PDF — AES-256 encryption, the strongest standard version in common use. Set a password, download, and the file simply refuses to open without it in any viewer, on any device.
Key Facts
- AES-256 — the strongest encryption mainstream viewers accept
- Password required to open, enforced by every compliant viewer
- Zero-knowledge: password and file stay in your browser
- No signup, no watermark, no size games
Frequently Asked Questions
How do I password-protect a PDF for free?
Upload it here, type the password twice, and download the encrypted copy. The tool applies AES-256 encryption locally in your browser — the file is never uploaded anywhere.
What encryption does this use?
AES-256, applied by qpdf compiled to WebAssembly. It is the same cipher Acrobat uses for its strongest protection and is supported by every mainstream PDF viewer.
Can the password be removed later?
Yes — anyone with the password can decrypt the file, and our Unlock PDF tool does exactly that. Protection controls who can open the file, not what the owner can do with it.
I forgot my password. Can you recover the file?
No, and be suspicious of any tool claiming otherwise for AES-256. Recovery is mathematically infeasible — that is the point of the encryption. Keep a copy of the password somewhere safe.