This property determines the current encryption settings. When
you save the document the encryption settings - if any - will be
used to determine the method of encryption to be used.
By default documents are not encrypted when created. However if
you read an existing PDF document the encryption property will be
updated to reflect the encryption settings used to create the
PDF encryption supports two different types of password - a user
password and an owner password. You can use either password to open
and view the document. However unless you supply the owner
password, permissions will be applied and access to the document
may be restricted.
Typically PDF encryption is used to apply permissions to a
document. The user password is left blank and only an owner
password supplied. PDF readers will not prompt for a password if
there is no user password. However any permissions will
automatically be applied. In this way you can allow anyone to open
the document but restrict access to operations like copying text,
printing the document or extracting images.
Please note that you are legally bound to respect the
permissions present in existing PDF documents. For details please
see the Legal Requirement