Best way to do this?

I am a newbie. I have a couple of pdf forms that are posted every 3
months with some changes. I want to fill in the text boxes on those
pdf forms by using a rails application. So this is what I was
thinking. I create a table for the pdf forms. And I create a table for
all the fields that need to be filled out on the form. As part of
those fields I create positioning coordinates for each field to lay
all the text boxes into their appropriate location ontop of the pdf
document. Then merge the two.
Would this be a way to do this or is there a better way?