A basic manual is available at http://www.aksdb.de/CentrED/Manual.pdf (http://www.aksdb.de/CentrED/Manual.pdf)
It is far from complete but should give a small insight to the program and its setup.
Also, Peter (//http://www.aksdb.de/board/memberlist.php?mode=viewprofile&u=64) put together a very good Czech manual. You can find it here:
http://robinzloxly.wz.cz/formats/index.html (http://robinzloxly.wz.cz/formats/index.html)