What a password on a PDF does
After protecting, the PDF opens only for someone who types the password. Without it, the contents can’t be read at all: they’re encrypted with AES-256, the strongest encryption the PDF format offers. Current PDF readers, like Adobe Reader, Chrome, Edge and Preview on a Mac, open it once the password is typed.
The encryption runs on your device. The file and the password are never sent to us, so we have nothing we could open.
Choosing a password
If you make up your own password, you type it twice, so a typo can’t lock you out of your own file. Under 8 characters, you’ll see a warning: short passwords are easy to guess, and 12 characters or more is much safer.
Stuck for one? Press Suggest a strong one. You get four random everyday words and a number, like maple-otter-canvas-orbit-47. That format is deliberate:
- it’s strong. There are over 100 trillion possible combinations, far more than anyone would try for an everyday document. For something very valuable, add a word of your own;
- it’s easy to pass on. The person receiving the PDF often has to type the password on a phone, or hear it read out on a call. “Maple otter canvas orbit 47” survives a phone call; “xK9#mP2$” doesn’t.
A suggested password is shown in full with a Copy button, and you don’t need to type it twice. It appears again on the result screen so you can note it down. Press Another one for a different suggestion.
Stopping printing or copying
Under Stop printing or copying you can also stop the PDF being printed, or stop text and pictures being copied out of it. Be realistic about these. Most PDF apps, like Adobe Reader and Chrome, respect them, but a few ignore them. They slow people down; they can’t stop someone determined. The open password is the real protection.
Sending a protected PDF
Don’t put the password in the same email as the file. If the email is forwarded or the account is hacked, both go together. Send the password a different way: a text message, WhatsApp, or a call.
If you forget the password
We can’t recover it, because it never left your device, and with a strong password nobody else can either. Keep your original, unprotected file somewhere safe, or store the password in a password manager.
You download a copy named like contract-protected.pdf. To remove the password later, use Unlock PDF. If the file should also carry a visible mark of who it’s for, add a watermark before protecting it.
Checked against the tool on 22 October 2026. How we write and test these guides