Sending a payslip, bank statement or contract by email? Adding a password means only someone who knows it can open the file, even if the email is forwarded or the attachment ends up in the wrong place.
Two kinds of PDF password
- Open password (user password): needed to open and read the document. The content is encrypted, so this is real protection.
- Permissions password (owner password): lets anyone open the file but restricts printing, copying or editing. Many apps respect it, but it's easy to remove, so don't rely on it for secrets.
How to add a password for free
- Open the Protect PDF tool and choose your PDF.
- Type a password twice.
- Choose whether people can print, copy or edit after opening it.
- Download the protected copy. It's encrypted with AES-256 in your browser, so the file and password aren't uploaded.
You can also add a password from Microsoft Word on Windows (Save As → PDF → Options → “Encrypt the document with a password”) or from Preview on a Mac (File → Export → Encrypt).
How strong is it?
AES-256 itself can't realistically be broken. The weak point is the password: tools that guess passwords can try millions of common passwords quickly, so a short or predictable password can be found.
- Use at least 12 characters, or a passphrase of four random words.
- Don't use names, birthdays or phone numbers.
- Get a strong one from the password generator.
Sharing the password safely
Never send the password in the same email as the file. Send it by text message or phone call, or agree on it in advance. And keep an unprotected copy yourself: if the password is forgotten, the file can't be recovered.
To remove a password later, when you know it, use Unlock PDF.