PDF Encrypt Tool can be used to protect your PDF files with 128-bit strength user and owner passwords, set all permissions(such as coping, editing, printing, selecting text and graphics, fill in etc), and prevent PDF files from being printed, changed, copied, extracted, signed, filled, assembled and/or merged. It is a shareware PDF encryption application that's straightforward, easy-to-use, light on system resources, reliable and easy to setup.
Here is a screenshot to illustrate the features and user interface of this application:
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