This is wholly my own personal selection, based fairly narrowly on how capable I find these applications to work with Scribus for print. If you disagree, I most certainly will listen to a well reasoned argument. Be prepared though! Part of my day job is to evaluate similar commercial applications for clients. Some of these apps have been tested within the limitations of modern PC hardware. Example: Telling Xnview to create 10,000 thumbnails at once. So in alphabetical order:
One of the challenges with PDF and EPS viewers on Linux, is that Scribus creates high end PS level 3, PDF 1.4 and PDF 1.6 in the future. Sometimes these features are beyond the capabilities of some open source viewers. Some of these features are necessary for reliable commercial printing and only supported in commercial pre-press or DTP tools. Four years of working with Scribus has led me to the strongly held conclusion that the following three viewers are the most reliable at displaying PS/EPS/PDF created by Scribus:
pstoedit and epstool. For more detailed notes and hints: GSview. I consider it an essential tool for DTP on Linux.If any other PDF or EPS viewer you choose cannot display PDFs from Scribus, but they do view properly in Acrobat Reader 5+, file a bug with the upstream author. I cannot stress this enough. In virtually all cases I have tested, it is a limitation of the viewing application. Scribus PDFs are tested daily with specialist pre-press software to validate their adherence to the published PDF specifications.