One of the main reasons why PDF is a hugely popular document format among computer users is related to its easy to customize security settings.
As easy as they are to setup, the restrictions assigned to PDF files can also be removed by other users, provided that they have the appropriate app.
Such tools will offer one the option to easily remove the user and owner passwords, as well as to disable the printing or editing restrictions.
In order to make sure that the PDF file will not be unlocked, users may also rely on apps capable of encrypting the PDF file before distributing it.