I am looking for a platform to build a manual and function reference for my open source software-in-development. Something that is easily organized. I spotted a very nice and simple solution here:

mpdf1 . com/manual/index.php

But contacting the author has not resulted in information what that software is and by the look of it, it looks custom. I suppose a Wiki could do that job in a way, but a Wiki is not exactly the thing I am looking for.

Any assistance would be welcome, this was a very tough topic to search in Google considering that reference and manual often led to actual programming language references and manuals.