How to Password Protect a PDF

PDF password protection isn't one feature, it's two, and confusing them is the most common mistake people make when trying to secure a document.

Open password vs. permissions password

An open password (sometimes called a user password) prevents anyone from opening the file at all without entering it first. A permissions password (or owner password) lets anyone open the file, but restricts what they can do with it, like printing, copying text, or editing. If you actually want to keep a document confidential, you need an open password, not just a permissions password.

Choosing a strong password

A short password on a PDF is weaker than it feels, since PDF passwords can be cracked with brute-force tools, especially older PDF encryption standards. Aim for at least 12 characters mixing letters, numbers, and symbols, and avoid anything related to the document's content, like a company name or the year.

Setting permission restrictions

Beyond the password itself, most protection tools let you separately restrict printing, copying, or editing. These restrictions are useful for things like preventing casual copy-pasting of a contract, but they're not a strong security measure on their own since permissions restrictions can be bypassed more easily than a genuine open password.

Sharing a protected PDF safely

Never send the password in the same email as the protected file. Send the file first, then the password through a separate channel, like a text message or a phone call, so that anyone who intercepts one doesn't automatically get the other.

Removing protection later

If you set a password and later need to remove it, you'll need the original password to unlock the file first. There's no legitimate way to remove a PDF password you don't know, which is exactly the point of the feature, so keep your passwords somewhere you won't lose them.