Producing pdf docs, best strategy

I would like to produce simple ‘contracts’ based on data stored in a DB
and a standard template
(simple : few data , name / address / dates … and one standard
template document )

I can use PDF Writer or XML-FO, but I don’t know the pro-cons of

in the firts version the user will not have the capability to modify the
texts in the template, but maybe in a second version… does it influence
the choice ?

thanks for your suggestions