Evince - Evince is a document viewer for multiple document formats: PDF, Postscript, djvu, tiff, dvi, XPS...
WinDjView - WinDjView is a fast, compact and powerful DjVu viewer for Windows with tabbed interface, continuous...
Okular - Okular is a universal document viewer based developed by KDE.
DjVuLibre - DjVuLibre: Open Source DjVu library and viewer
MuPDF - MuPDF is a lightweight PDF and XPS viewer.
Foxit Reader - Foxit Reader is a free and light-weight multi-platform PDF document viewer.