Since late 2014, Adobe's proprietary but useful Adobe Acrobat Reader DC has been no longer supported under Linux. Adobe's website still only lists Windows, Mac OS and Android as supported operating systems. This is one of the many dangers of closed source software - at the whim of corporate bosses, development and distribution can simply disappear overnight, possibly never coming back. Fortunately, there are some excellent open source alternatives to Adobe Acrobat Reader DC. The software featured in this article offer more than displaying PDF files; they are versatile document viewers.