Linux and SuSE aren't going to do anything to your KWord files. However you will find that the KDE settings that are stored in your user directory, under $HOME/kde, will be changed by the new version of KDE. That is because the new version of KDE uses different settings and files to store those settings. It really made me angry when I installed SuSE 10.1 and tried to keep the system dual boot with SuSE 9.2. The first time that I ran KDE under SuSE 10.1 it changed the KDE settings in my user directory. When I booted to the old version of SuSE then the old version of KDE didn't run well at all. So you might find a few little problems with having some of your KDE settings changed. You may have to reset some of your preferences. Otherwise your data will be undamaged. It shouldn't be a problem, just a little nuisance the first time that you run KDE.
I advise against trying to upgrade. I never ever upgrade. I always install a fresh version of Linux and go through all of the tedious configuration stuff. The reason that I never upgrade is that things never work as expected anyway. Features that have changed and that should have been altered appropriately never are changed appropriately. It is just as much of a nuisance to try to fix all of the problems created by upgrading as it is to just reconfigure a raw installation. Just make sure that you don't reformat your data partition. And make a backup of your data before you do anything else.