How to highlight text in PDF files in Linux [closed]
Solution 1:
You can use okular for that purpose. Be aware that it doesn't actually change the PDF. The annotations are stored in a separate file and can (only?) be displayed by okular.
screenshots
Solution 2:
Another option is Xournal (article on Wikipedia).
Solution 3:
Have you had a look at Jarnal as a rather cool general note taking tool (and its cross platform)?