Use the right check
Protect PDF requires a password of at least eight characters and has no built-in default. After exporting, close the document and reopen it in another reader. Confirm that an incorrect password is rejected. Keep an unencrypted source in a secure place if you will need to edit it later.
Unlocking needs authorization
The unlocking tool uses a supplied password and creates a fresh unencrypted page copy. It stops on a wrong password instead of ignoring encryption. It is intended for documents you own or have permission to modify, not password cracking.
Know the limits
A password cannot prevent an authorized recipient from copying visible information. Page copying may also omit forms, bookmarks and other document-level features. Editing a signed PDF can invalidate its existing cryptographic signature. Ask the recipient which security settings they require.
Try the related tools
Further reading
Updated 2026-10-18. These are implementation notes and practical explanations, not a conformance certificate.