You can use LibIconv for that: http://www.gnu.org/software/libiconv/ Convert from UTF-8 to iso-8859-1. It's a command line tool, so you will need some kind of script to mass convert all your topics.
But can't you reconfigure the server application to work correctly with UTF-8? Otherwise you will need to convert all your output files every time you create an output.
Thanks for the ideas!
@Peter: Nah, that's way too easy. Can't believe I missed that
Nah, that's way too easy. Can't believe I missed that
Yep that did the trick. It's a new feature and I did not notice it yet.