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.

There are three 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, and AES encryption (method AES) in Acrobat 7 (PDF 1.6) and above.

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.