PDF encryption (password)
Also known as: password-protected PDF, PDF password, encrypt PDF
PDF encryption scrambles a PDF’s contents so it can only be opened or edited with the correct password. There are two kinds: a user password to open the document and an owner password that restricts actions like printing, copying, or editing.
- User password encrypts and gates opening the file
- Owner password restricts printing, copying, or editing
- Strong (AES) encryption protects a password-locked PDF
Open passwords vs permission passwords
A user (open) password encrypts the whole file — without it, the contents stay unreadable. An owner (permissions) password leaves the PDF viewable but blocks specific actions such as printing, copying text, or modifying the document.
Modern PDFs use strong AES encryption when a user password is set, so a well-chosen password genuinely protects the file. Permission-only restrictions are weaker, since the document still opens freely.
Adding and removing protection
Encryption does not meaningfully change file size; it protects access, not space. Keep the password somewhere safe — a forgotten open password cannot simply be reset.
To add a password, /tools/protect-pdf encrypts the file; /tools/unlock-pdf removes encryption from a PDF when you already know the password.