Hi. I discover an excellent PDF editor. It is jPDF Tweak. It is a portable java application.
It's sites:
http://jpdftweak.sourceforge.net/
&
https://sourceforge.net/projects/jpdftweak/
Last developer update at 19 / 1 / 2017
Currently it does not support editing in Arabic characters in watermarks & document info (though it display them correctly ! I feel this application could be a great tool with further development.