You set a password on a PDF six months ago to be safe. Now you need to open it and have absolutely no idea what the password was. The honest answer about recovery depends entirely on what kind of lock you used.
Permissions locks: usually recoverable
A permissions password restricts editing, printing, or copying — but the file still opens. If you can open the file but can't edit it, unlock PDF lifts the restriction in seconds. These locks are by-convention; PDF viewers respect them, but the encryption is weak. Flint handles this safely for files you own — provide proof of ownership if asked, and the lock comes off.
Open locks: usually unrecoverable
An open password encrypts the file itself. Without the password, the contents are mathematically scrambled. Modern PDFs use AES-256, which is genuinely unbreakable in human time scales. If you've lost an open password, the file is effectively gone. Don't pay 'PDF password recovery' services that promise miracles — most are scams or malware. The only honest path is to recreate the document from the source.
Avoiding it next time
Use a password manager (1Password, Bitwarden, your browser's built-in one). Store the password the moment you create it, alongside the filename. Future-you will save current-you's bacon. For PDFs you'll definitely need later, consider storing an unprotected copy in a secure backup — and only protect the version you send. The 'master' stays accessible to you.
FAQ
What about online password crackers?
Effective only for weak passwords or very old PDF encryption. Modern AES-256 with a strong password genuinely cannot be cracked. Don't pay anyone who claims otherwise.
Can the original sender unlock it?
Only if they remember the password they set. PDF passwords aren't recoverable from the file itself, even by the original creator. Ask anyway — sometimes the password was simple and they recall it.
What's the difference between unlock and crack?
Unlock PDF removes weak permissions locks legitimately on files you own. 'Cracking' implies bypassing strong encryption on files you don't own — that's neither legal nor usually possible.
Permissions locks lift in Flint. Open passwords are forever. Use a password manager next time.