STDU Viewer is described by its author as
View all most popular documents formats by one program.
STDU Viewer supports many text based formats and can present them in an unobtrusive and somewhat attractive interface. It tries to centralize the task that may require several programs. For example notepad to open *.txt files and a PDF viewer to open *.pdf files. To that end STDU Viewer supports TXT, TIFF, PDF, DjVu, CBR, CBZ and XPS file formats.
The program has some interesting and useful features that perhaps make it more useful for some. Using the View menu it is possible to enable navigation tabs (see image) which will appear to the left of the document. Here one can search the document, view thumbnails of its pages, view its contents or bookmark a page. The latter is possible via a right click on the desired page or location of a document. Also within the View menu is the ability to rotate pages of the document. Perhaps more interestingly the Setting option, again residing under the same View menu, lets the user change the brightness, gamma or contrast of a document, this can prove useful when viewing poor quality documents or getting a better view of embedded graphics.
STDU Viewer works on Windows 2000, XP, 2003 and Vista. It is free for non-commercial use.