you use acrobat to alter your pdf to allow form input with it, that is a 'submit' button.
then you enable your rails application to load that pdf in your browser.
It will be opened with acrobat reader plug in; that's why you need that submit button - acrobat reader doesn't allow save action.
in the background you have a database tabel, such as mysql. the field names in the database must match the field names on the pdf.
When you push submit you need an action that saves the acrofield data to the database.
once in the database, you can recall those data and fill a template with it.
for this you need
pdf/stamper - ruby forge
if you get all that together it is finally a simple method in your controller to generate a output.pdf that merges your db record set with the