precision alignment of text using x,y coordinates?

I am attempting to fill in a printed form using this library.

I realize it that the x,y are in points and those are 72/inch. However, that is to the top of the text. How can you calculate where the bottom of the font would lie? I assumed it would be using the heightOfString() method, but subtracting that off the y coordinator still doesn't line up how I need it do?