How can I encrypt my PDF documents in a simple way?

I have made a PDF document and would like to protect it with a password. How can I encrypt my pdf document in a simple and easy way? Any good suggestions? I not only want to add password to pdf, but also want to set restrictions to pdf file, like this screenshot shows:


Some people recommend me to use WowTron PDF Encryption which is a powerful pdf encryption software.

Step1: Download WowTron PDF Encryption: 

Please download and install the app, it will take you 10 seconds.

Step2:ImportPDF Files

Ater installing the software, you can add pdf files.

Step3:Add password to pdf files.