Creative Commons Share Alike 3.0
The
Comic Book Archive (.cb7, .cbr, .cbt, and .cbz)
Device Independent file format (.dvi)
DjVu (.djvu, .djv)
Open XML Paper Specification (.oxps, .xps)
Portable Document Format (.pdf)
PostScript (.ps)
In some Linux distributions, not all formats are supported by default, so you might not be able to view all the formats listed above.
Support for a format is called a backend. If you get the error "Unable to Open Document", you may wish to check whether the backend package for the format is installed.