People sometimes like to edit PDF documents. KWord has the ability to import, edit, and re-export PDFs, but the formatting often gets messed up during import. pdfjam is a command-line tool that allows you to do some sophisticated PDF manipulating (rotating, combining, splitting), but it also has limitations, and sometimes people are more comfortable with a point-and-click graphical user interface (GUI).
The pdfedit package is no longer available in the Ubuntu repositories as it depends on old qt3 libraries that Ubuntu no longer provides.
Consider this post on Ask Ubuntu.
Afterwards, you should be able to launch PDFedit with the command