Looking for an app to edit PDF on Linux?

I’ve been on the lookout for an application that will allow me to make quick notes and things to pdf-presentations. As a student, this is invaluable to me. I have been fiddling a little with pdfedit before, but finally I’ve found the grail. It is Xournal, and I found it after I bought a wacom tablet. It’s right in Ubuntu’s repositories too. From the package description: “Xournal is a GTK+ application for notetaking, sketching and keeping a journal using a stylus. It can also be used to add annotations to PDF files.”