How to protect PDF
- Open the PDF you want to protect.
- Type a password, and type it again to confirm.
- Download the protected PDF.
- Send the password to the recipient separately, for example by text or a phone call.
What password protection does
The PDF is encrypted with AES-256, a strong and widely used encryption standard. Without the password, the file is scrambled data and PDF readers will not show the pages. Anyone who opens it needs the password, whether they get the file by email, a shared drive or a lost USB stick.
This is useful for payslips, P60s, bank statements, medical letters and anything with a National Insurance number. The encryption runs in your browser, so the unprotected file is never uploaded to be locked.
How strong should the password be?
Encryption is only as strong as the password. Someone with a copy of the file can try passwords over and over on their own computer, with no lockout. Short or guessable passwords, such as a name, a date of birth or "password123", can fall quickly.
Length beats cleverness. A passphrase of four or more random, unrelated words, such as "copper lantern whistle marmalade", is far harder to guess than a short jumble like "Tr0ub3e", and easier to type and read over the phone. Avoid anything the recipient or an outsider could find out, like a postcode or pet's name.
- Send the password by a different route from the file.
- Use a different password for each document you send.
- Keep the password somewhere safe, such as a password manager.
If you forget the password
We cannot recover it. Nothing is stored on our side, and strong encryption has no back door. Keep your unprotected original until you are sure the password is saved.
Questions people ask
Can I remove the password later?
Yes, if you know it. Unlock PDF saves a copy that opens without a password.
Will the recipient need special software?
No. Standard PDF readers, including the ones built into phones, browsers and computers, ask for the password and then open the file.
Is it safe to email a password-protected PDF?
It is much safer than sending it unprotected, as long as the password is strong and sent separately, not in the same email.
What if I forget the password?
It cannot be recovered by us or anyone else, so keep a record of it or keep the unprotected original.