I was wondering if there is a pdf reader-writer-publisher-editor that can add text, highlight, shapes and general edit an existing pdf document.
Something like Nitro in windows.
There are several options out there, none of which come close to the functionality of editors such as Adobe Acrobat or Foxit PDF Reader under Windows. That's why I prefer to run Foxit via PlayOnLinux.
As far as native applications are concerned, Master PDF Editor is probably the most advanced PDF editing suite available in Ubuntu right now. It's available for free from the Ubuntu Software Center but requires you to register an account with Ubuntu before installing.
LibreOffice 4.0 opens PDF files in LibreOffice Draw where you can make all kinds of edits. I just used it to enlarge 80 images and move them around; it worked great!
If you are using Ubuntu 12.04, 12.10, or 13.04 then you probably have version 3.5, which does not have this feature. As I did, you can now force Ubuntu to upgrade to version 4.0 by typing the following in a terminal (press enter after each line).
If you don't have LibreOffice installed for whatever reason, then instead of the last line, type this.