Password protect a PDF
Encrypt a document so it cannot be opened without your password.
- Runs on your device — the file is never sent anywhere
- No sign-up, no watermarks, no daily quotas
- Free, with no limit on how often you use it
How it works
Password-protecting a document is something you do because its contents are private. Uploading that same document, and often the password, to a website in order to protect it is a contradiction most people notice only afterwards. This encrypts it in the page.
Real encryption, not a setting
The document is encrypted with AES, the same cipher standard used for protecting classified material. Without the password the file cannot be read — not by a different PDF reader, not by us, not by anyone. That is what makes it worth doing and also what makes losing the password final.
AES-256 or AES-128
256-bit is stronger and is what every current PDF reader supports. 128-bit exists for very old software; choose it only if something refuses to open the 256-bit file.
Your password is the weak point
The encryption is not breakable, but a guessable password is. A short or common password can be attacked offline for as long as an attacker likes. Use a long passphrase, and use the password strength checker here if you are unsure — it also runs on your device.
Printing
You can allow or forbid printing. Be clear-eyed about this: restrictions like these are honoured by well-behaved readers and are trivially bypassed by software that chooses not to. The password is the real protection; the permissions are a courtesy.
Password protect a PDF — questions
Can you recover my document if I forget the password?
No. There is no reset and no back door — the encryption is real and the password never left your device.
Which encryption is used?
AES-256 by default, with AES-128 available for older readers.
Is my document uploaded?
No. It is encrypted in your browser by qpdf compiled to WebAssembly.
Do the printing restrictions actually stop anyone?
Not determined software. They are honoured by many readers, though some ignore them; the password is the real protection.