PDF Lock — Free Online Tool
Password-protect any PDF with real AES-256 encryption. The password is applied inside your browser and never sent anywhere.
Your file
Set a password
How it works
Real AES-256 encryption
Not a fake lock — industry-standard 256-bit encryption, the same level banks and governments use.
Password never leaves you
Encryption runs entirely in your browser. We never see, store or transmit your password or your file.
Instant & free
No sign-up, no watermarks, no file-size games. Lock as many PDFs as you like.
Frequently asked questions
Is this real encryption or just a fake lock?
Real. Your PDF is re-written with AES-256 encryption — the same standard used by banks and governments. Without the password, the file's content is unreadable in any PDF reader.
What happens if I forget the password?
There's no way to recover it — not even by us, because your password never leaves your browser. Keep it somewhere safe before you lock important documents.
Are my PDF files uploaded to a server?
No. Everything happens inside your browser using a client-side encryption engine. Your files and your password never leave your device — not even temporarily.