Password Protect a PDF

Open password vs. restrictions: what's the difference?

A PDF can carry two passwords. The open password, also called the "user" password, is required as soon as someone opens the file: without it, the content stays encrypted and unreadable. That's the real protection, the one to use for a pay stub, a bank statement, a tax return or medical records you send by email. The owner password sets permissions instead: blocking printing, text copying or editing. The document then opens normally, but the reader enforces your restrictions. Most apps respect them, but not all of them do, so for a confidential document, rely first and foremost on the open password.

How to choose a good password for a PDF

AES-256 encryption is extremely strong: the weak spot is almost always the password. A first name, a birthday or "123456" are on the lists that cracking software tries first. Aim for at least 12 characters mixing uppercase, lowercase, numbers and symbols, or a passphrase of four or five unrelated words, such as "giraffe-drum-storm-lemon." The "Generate a strong password" button creates 16 random characters, out of reach of brute-force attacks. When you send the file, share the password another way, by text message or in person, never in the same email as the attachment.

Lost password: why nobody can reopen the file

With an open password, the PDF's content is truly encrypted: it's not just a lock that someone could get around. Chatzam never keeps your file or your password, since everything happens in your browser, so there is no way to recover it, not for us and not for anyone. Always keep an unprotected copy of the document somewhere safe and store the password in a password manager. To remove the protection later from a PDF whose password you know, use "Unlock PDF." And to shrink a file that's too large, run it through "Compress PDF" before protecting it.