AES encryption

AES (Advanced Encryption Standard) is the encryption that protects a password-secured PDF. When you lock a PDF, the actual page content is scrambled with AES, typically a 256-bit key, so the data is unreadable without the password. It is the same proven, government-grade cipher used to protect everything from banking to messaging.

This matters because there are two very different ways to secure a PDF. A simple permissions flag just politely asks viewers not to print or copy and is trivial to bypass. Real AES encryption actually transforms the bytes: without the key, there is nothing to read, period. That is the difference between a sticky note and a locked safe.

PDF supports two kinds of password: a user password to open the file at all, and an owner password to control printing, copying, and editing. For anything sensitive, contracts, medical records, payroll, AES encryption is what keeps it private if the file ends up in the wrong hands.