If you want to add comments / notes and highlight text in Linux with a native PDF viewer Okular is your huckleberry
Note: I found that you have to do a File ==> Save As and resave PDF documents annotated with Okular in order to be able to view the annotations in Acrobat Reader / Gnome Document Viewer otherwise the annotations are only visible when you view in Okular.
|Adobe Acrobat Reader 9.5.5
|Document Viewer (Gnome default)
|Okular (KDE PDF Viewer)