You try to copy text from a PDF and nothing happens. Or you try to edit a form and it says 'permission denied'. The PDF isn't broken — someone locked part of it on purpose.
Two kinds of lock
PDFs have open passwords (you can't open the file without one) and permissions passwords (you can open it but can't print, edit, or copy). Permissions locks are common on bank statements, ebooks, and contracts where the sender wants you to read but not change. If you own the document and lost the password, unlock PDF can lift permissions locks. Open passwords are stronger and usually require the original sender.
Why senders lock things
Banks lock statements so account details can't be tampered with. Publishers lock ebooks to discourage copy-paste piracy. Lawyers send signed contracts as locked PDFs so the agreed wording stays put. Most locks are about preserving a version, not blocking you from reading. If you need to fill in a locked form, the sender probably forgot to set it to fillable — ask for an unlocked version rather than working around the lock.
When you should leave it alone
If a PDF is locked and isn't yours, don't try to crack it. Ethical use of /unlock-pdf is limited to your own files or files you have explicit permission to modify. Most of the time, asking the sender for an editable version takes thirty seconds and avoids any awkward questions.
FAQ
How can I tell if a PDF is locked?
Most viewers show a padlock icon in the title bar or sidebar. Try to copy text or print — if those options are greyed out, it's permissions-locked. If you can't even open it without a password, it's open-locked.
Can I lock my own PDF?
Yes — use password-protect PDF to add either an open password, a permissions password, or both. Useful for sharing sensitive documents over email.
Does locking a PDF make it secure?
It raises the bar but isn't unbreakable. For genuinely sensitive data, combine locking with a secure transfer method (encrypted email, secure portal) rather than relying on the PDF password alone.
Locks are usually intentional. If it's your file, Flint can unlock it; if it's someone else's, the polite path is to ask.