This post can now be read at HERE
Recently someone asked this question to me and after some search on Google I came across mentions of PDFedit, Scribus, flpsed, Gimp, PDFMod and even the openoffice plugin for importing PDF and I tried all of these. PDFescape is probably a good solution but is only online and limited to 30 pages in it's free avatar. If your aim is similar to the one stated below, these tools are way too complicated (PDFedit), limiting (PDFescape) or ineffective (rest of them).
So, Let's start with the usual what was my aim question.
To be able to highlight and put his own annotations, highlights and comments in the lecture notes that he gets from his college lecturers in pdf and be able to print the amended notes from any platform. (Linux / Mac / Windows.)