Password-protect a PDF
A lock on the document: the file is closed with a password asked for at opening, and the encryption happens on your device. Handing a sensitive document to a server in order to secure it has always been the paradox of these tools — here, there is no server.
Free · 100% local — nothing is uploaded- 1Open the document to protect.
- 2Choose the password.
- 3Download the encrypted PDF.
How to password-protect a PDF
Open the document, choose a password, download: the resulting file is encrypted and asks for that password at opening, in Acrobat as in a browser or on a phone. The encryption is computed on your device, with AES-256, and the password is neither transmitted, nor stored, nor recoverable — which is the very definition of encryption worth the name. Take a moment to weigh the paradox of the other services: to secure a confidential document, they ask you to upload it to their servers. Here there is no server to entrust it to. Choose a long phrase rather than a short word, and pass it along by a channel other than the one carrying the file. Choose a long phrase rather than a word: it is the only thing standing between your document and a stranger.
Preventing copying, printing, editing
The PDF format also provides for usage restrictions — barring printing, copying the text, editing — attached to the document. They are respected by readers that play the game, and got around by those that do not: they are instructions, not locks. The only real lock is the opening password. To freeze annotations or a completed form without imposing a password, flattening is what you need.
Frequently asked questions
Is the password sent anywhere?
No. It never leaves your browser, and the encryption happens there too.
What happens if I forget the password?
The document becomes unreadable, for you as for anyone else: that is what encryption is. Write it down elsewhere before closing the page.
Which encryption is used?
AES-256, the PDF format’s standard encryption: Acrobat, Preview, browsers and recent readers open it with no special software.
How long should the password be?
A phrase rather than a word: four unrelated words beat one complicated eight-character word, and they can be remembered. Encryption is only ever worth as much as its password.
Can I send the file and the password together?
That is the gesture that cancels everything out: both travel down the same channel, so a single interception is enough. Send the password another way — a message, a call.