I am not using KDE right now, so I am not sure. You may have to wait for one of the KDE guys to pick up this thread. At least you know it works (in GNOME), so that may be a consolation.
The last time I was using KDE was in openSUSE. I know I used YaST and CUPS to configure the printers that way, plus there was a program called HPLIP, too. If it works in GNOME, it certainly should work in KDE - especially with Mint. Are you having fun yet? Good luck!