I tried now for hours and can not figure out how this is supposed to work.
The Doc PDF is shame as the index is wrong and it seems the figures not always match with the text. Time to rework it, I guess.
EDIT: It seems to work, guess I checked only as admin and for this role, there is now rewrite of the link URL ... ok. Meanwhile I also deleted a rewrite rule from the .htaccess which belonged to the other download mananger. This could also made it work now?