Glossary / PDF Encryption
What Is PDF Encryption?
PDF encryption is a security feature that restricts access to a PDF document using passwords and cryptographic algorithms. It can prevent unauthorized users from opening a file (user password) and restrict actions like printing, copying text, and editing (owner password).
How PDF encryption works
The PDF specification (ISO 32000-2) defines several encryption methods. Older PDFs use RC4 encryption with 40-bit or 128-bit keys. Modern PDFs use AES (Advanced Encryption Standard) with 128-bit or 256-bit keys, which is significantly more secure.
A PDF can have two passwords: a user password required to open the document, and an owner password that controls permissions like printing, copying, and modification. If only an owner password is set, anyone can open the file but restricted actions are blocked by compliant readers.
When to use encryption
Encryption is essential for sensitive documents such as financial statements, medical records, legal contracts, and confidential business reports. For maximum security, use AES-256 encryption with a strong user password.
Related tools on fixtdoc
- Protect PDF , password-protect a PDF with permission controls
- Unlock PDF , remove password protection from a PDF