NeeView - Display two images simultaneously
Okular - Okular is a universal document viewer based developed by KDE.
Soda PDF 3D Reader - Read any PDF document like a book using our patent pending 3D technology!
Sumatra PDF - Sumatra PDF is a slim PDF/DjVu/EPUB/XPS/CHM/CBR/CBZ/MOBI viewer for Windows.
ACBF Viewer - Comic book reader.
Foxit Reader - Foxit Reader is a free and light-weight multi-platform PDF document viewer.