How to lock a PDF

Put a password on a PDF so only the right people can open it.

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Locking a PDF means encrypting it so it cannot be opened, or edited, without the password. It is the right step before emailing a payslip, a contract or a bank statement — and it is genuine encryption, not a setting a viewer can ignore.

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How to how to lock a PDF

  1. 1Open the PDF you want to lock.
  2. 2Choose Protect and set a password.
  3. 3The file is encrypted with AES-256.
  4. 4Download it and share the password separately from the file.

Questions people ask

What is the difference between locking and flattening?

Locking encrypts the file so it cannot be opened without the password. Flattening leaves it openable but makes the content non-editable and non-selectable. They solve different problems and can be combined.

Can I lock a PDF against editing but still let people read it?

Yes — that is an owner password, which permits opening but restricts changes. A password to open is a user password. Choose based on who you are protecting it from.

What happens if I forget the password?

Nothing can be done. That is what real encryption means; there is no recovery, and any tool claiming otherwise is either breaking the encryption or not really encrypting. Keep a copy of the password somewhere safe.

Does it work on a phone?

Yes, it runs in a mobile browser with nothing to install.

Should I email the password with the file?

No. Send it by a different channel — a message or a call. A password in the same email as the file protects nothing.

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