Lock / Unlock PDF

The PDF specification (ISO 32000) defines a unique dual-password security system. A single PDF can have two different passwords, granting different levels of access.

• The User Password (Open Password): This is the password required just to open and view the document. If a PDF has a User Password, the entire file (text, images, and metadata) is mathematically encrypted. You cannot bypass this. Without the password, the data is just random noise.
• The Owner Password (Permissions Password): This password is used to restrict what you can do after you open the file. It controls a 32-bit integer flag inside the PDF called the P (Permissions) flag. This flag dictates whether printing, copying text, or editing the document is allowed.

If a PDF only has an Owner Password (meaning you can read it, but can't print it), this tool can strip those restrictions instantly.

Because the file is readable, the PDF parser can read the internal object streams. The "restrictions" (like blocking the print button) are entirely enforced by the PDF viewer software (like Adobe Acrobat) obeying the Permissions flag on the honor system.

Our tool simply parses the readable PDF, drops the encryption dictionary entirely, and saves a fresh copy of the data without the restriction flags.

Historically, PDFs used RC4 (40-bit & 128-bit), which is now considered cryptographically broken and obsolete.

The modern standard used by this tool when locking PDFs is AES-256 (Advanced Encryption Standard). As long as you choose a strong password, an AES-256 encrypted PDF cannot be brute-forced by any modern computer.