This tool is used to limit access to PDF documents, or some of its features, using password protection technology. For example, we can use passwords to restrict users from opening, printing, and editing PDF's. Only those who know the password will be able to access the protected feature.
The Compatibility option is used to control the version of the password protected PDF. Setting this is important if we need our file to be opened by old version readers. For more security, and more options, we should set it to the highest version available (as long as reader compatibility is not an issue).
The Encrypt level controls the type of algorithms used to encrypt the PDF. Higher levels improve protection to our files. Select the No security level if you want to remove passwords security from some, already protected, files. Only work if only the permissions password is set.
The Document Components to encrypt controls the document components that are going to be encrypted. The Except metadata option is useful if you want to protect your document, but also allows your file to be indexed by metadata content, by tools that do not know how to decrypt password encrypted objects.
If you set an Open Password your file can only be opened by someone that knows that password.
With the permissions options you can restrict print operations, print quality, contents extraction or document manipulation. These restrictions are only granted by the tools used to view the PDF's, and so there are no guaranties that they are going to be respected.