Is there one? I would search for one but as I don't know the model, revision etc. this may lead me the wrong way.
Found one here... geeetech.com/Documents/Rumba users manual.pdf but not checked it against the RepRap one, which must have been a lot lower in my search results.
Yeah but I wonder what you wanna do with it, it just describes the board. How to use it depends on what firmware you install... BTW the Marlin Project team started a documentation: https://github.com/MarlinFirmware/MarlinDocumentation viewable here: http://www.marlinfw.org