PDF encryption is baked into the format — every mainstream PDF viewer knows how to prompt for a password. The Rankato tool uses AES-256 (the strongest algorithm the PDF spec supports) and lets you set two passwords: an open password (required to view) and an owner password (required to change permissions). Choose either or both; the owner password alone restricts actions without requiring a passphrase to open.
Open vs. owner passwords
Open password: users must type it to view the PDF at all. Owner password: allows opening freely but restricts actions (printing, copying, editing). Most contract-sharing use cases want an open password; publishers who want to prevent copy/paste use owner passwords.
Permission flags
With an owner password set, you can restrict: printing (or high-res printing), copying text/images, modifying content, filling forms, adding annotations, extracting pages, and accessibility support. These are honored by well-behaved viewers but can be bypassed by determined actors — real security depends on the open password.
Password strength
The tool warns on weak passwords. For real security, use 12+ characters mixing letter cases, digits, and symbols. Short passwords (6-8 chars) can be brute-forced against the encrypted file offline.