If you're not using more than 4 different types of fonts, you don't even really need an addon to change them. Gonna copy/paste this info from
Vranx's site.
Create four copies of the font file of your choice, place them in \World of Warcraft\
Fonts folder, and rename them to the following names:
FRIZQT__.ttf (the main UI font)
ARIALN.ttf (the normal number font)
skurri.ttf (the 'huge' number font)
MORPHEUS.ttf (Mail, Quest Log font)
What I did is found one font from online that I liked, and renamed it to each of the above 4 fonts and stuck all 4 of them into that Font's folder.