Introduction

PDF files can be encrypted using various types of encryption and attaching various permissions describing what someone can do with a particular document (for instance, printing it or extracting content). There are two types of person:

The User can do to the document what is allowed in the permissions.

The Owner can do anything, including altering the permissions or removing encryption entirely.

There are five kinds of encryption:

• 40-bit encryption (method 40bit) in Acrobat 3 (PDF 1.1) and above
• 128-bit encryption (method 128bit) in Acrobat 5 (PDF 1.4) and above
• 128-bit AES encryption (method AES) in Acrobat 7 (PDF 1.6) and above
• 256-bit AES encryption (method AES256) in Acrobat 9 (PDF 1.7) - this is deprecated - do not use for new documents
• 256-bit AES encryption (method AES256ISO) in PDF 2.0

All encryption supports these kinds of permissions:

-no-edit	Cannot change the document
-no-print	Cannot print the document
-no-copy	Cannot select or copy text or graphics
-no-annot	Cannot add or change form fields or annotations

In addition, 128-bit encryption (Acrobat 5 and above) and AES encryption supports these:

-no-forms	Cannot edit form fields
-no-extract	Cannot extract text or graphics
-no-assemble	Cannot merge files etc.
-no-hq-print	Cannot print high-quality

Add these flags to the command line to prevent each operation.