PDF documents are at present the most popular form of distributing documents throughout the Internet and a presentation tool at the same time. They owe their popularity not only to well defined standard embracing text, pictures and hyperlinks, but foremost to the fact that once created they can be read under nearly every operating system and its underlying platform. Of course, to open a PDF document one has to have an appropriate application.
There are quite a few PDF readers (called PDF viewers as well), albeit the first, proprietary, and so called “official” PDF viewer is Acrobat Reader from Adobe Systems Inc. The company is also the father of the PDF format. The mere fact that the Acrobat Reader was an application with a closed source code didn’t appeal to many GNU/Linux admirers, and consequently led to the creation of multiple open-source alternatives. Viva l’difference! In this text I will describe the following readers: Acrobat Reader, Xpdf, KPDF, Evince, ePDFview and Okular.