You can install additional fonts e.g. to use in Abiword. Download TrueTypeFonts (TTF) from the internet and save the files into /usr/X11R7/lib/X11/fonts/TTF:
Click on the button "Select All" and then on the button "Extract". A new window appears.
Click on the button "Choose".
Go to the directory /usr/X11R7/lib/X11/fonts/TTF. Click on the button "Open".
Click on the button "OK".
Now the file is unpacked and the fonts will be copied into the directory. Do the same with all of your TTF-files. If you start Abiword afterwards, the fonts are available.