PDF files support two types of password protection, each serving a different purpose. Understanding the difference is essential for properly securing your documents — or recovering access to locked files you own.
User Password vs Owner Password
A user password (also called "open password") prevents anyone from opening the PDF at all. Without this password, the file is completely inaccessible. This is true encryption — the document content is cryptographically protected.
An owner password (also called "permissions password") allows the document to be opened and viewed, but restricts specific actions: printing, copying text, editing, form filling, and annotation. This is weaker protection — it relies on the PDF viewer respecting the restrictions.
PDF Encryption Standards
PDF supports several encryption levels. 40-bit RC4 (PDF 1.1-1.3) is weak and can be broken in minutes. 128-bit RC4 (PDF 1.4-1.5) is stronger but has known vulnerabilities. 128-bit AES (PDF 1.6) and 256-bit AES (PDF 1.7+) provide strong encryption that is computationally infeasible to break with current technology.
Protecting Your PDFs
When protecting a PDF, always use 256-bit AES encryption and a strong password (12+ characters with mixed case, numbers, and symbols). Set both user and owner passwords if you need both access control and permission restrictions.
Common Scenarios
Sharing sensitive documents: Set a user password and share the password via a separate channel (phone call, different messaging app).
Preventing unauthorized printing: Set an owner password with printing disabled. Note that tech-savvy users can bypass this using certain tools.
Protecting fillable forms: Use an owner password that allows form filling but prevents editing the form structure.
Protect your PDFs with our PDF Protect tool, or remove restrictions from PDFs you own with our PDF Unlock tool. Both work entirely in your browser for complete privacy.