How to improve the PDF document security

I signed a contract, then scanned to the computer and Packaged as PDF format. In this case, how to setup the PDF document for the tight
security allows the other to preview and print only and not allow to copy and edit its content? Moreover, the PDF document is not allowing to be converted to
other formats, like a Word Doc. PPT Doc and so on.

The contract is sent to me by e-mail as the JPEG format, I need to sign it on the printed paper and then reply to them by email again.