Open your PitBull settings and go to Target -> Other -> Auras, the option for Font Size is hiding there in the middle of the page. You may need to enable a configuration mode, or at least target something first, in order for the settings to show up.
You don't have all options visible. There should be an option to set how many buffs per row (or width of buff frame, whatever) offsets, etc. Are you positive that you are running the latest version and that you were in config mode when you looked?
That would be a no then. When you have issues, always get the latest version before asking for help. Also, double-check your version to be sure when someone asks you to make sure you have the latest version.