1) Free PDF reader 
Okular is the document viewer for KDE SC 4 (although it does not require the full KDE desktop). It is based on KPDF and it replaced KPDF, KGhostView, KFax, KFaxview and KDVI in KDE 4. Its functionality can be easily embedded in other applications. == History == Okular was started for the Google Summer of Code of 2005; Piotr Szymański was the acce...