How to password-protect a PDF

Guides · Updated 12 October 2026 · By Tiago Santos

A password on a PDF means a copy that gets forwarded, lost on a USB stick or left in an inbox can’t be read by whoever finds it. It takes a minute to add, as long as you understand the two kinds of PDF password.

Open password vs permissions

• Open password (also called user password): nobody can view the document without it. The contents are encrypted. This is the one that protects privacy.
• Permissions password (owner password): the PDF opens for anyone, but printing, copying or editing is restricted. Many programs ignore these restrictions, so treat them as a polite request, not protection.

How strong is PDF encryption?

Modern PDFs use AES-256, the same encryption used for banking. The weak point is the password. A short or common one can be guessed by software trying millions of combinations; a long, unique one cannot. Use at least 12 characters, or a few random words. Password generator makes one for you.

Add a password

1. Open Protect PDF and choose the PDF.
2. Type the password twice.
3. Download the protected copy. Keep the original somewhere safe, or delete it if the protected copy is the one you’ll keep.

The PDF is encrypted on your device. Uploading a confidential document to a website so that it can be protected would be an odd first step.

Share the password the right way

Never put the password in the same email as the file. Send it another way: a text message, a phone call or a messaging app. Anyone who gets into the email account would otherwise have both.

Not a PDF?

Lock file with a password encrypts any file, such as a spreadsheet, a photo or a ZIP, with AES-256. The person opens it with the same tool and the password.

Forgot the password?

If you know it, Unlock PDF removes it so you can save an unprotected copy. If it’s lost, there is no way back for anyone; that’s what makes the protection real.