Arguing that some changes to a reprint page or other elements could be changed.
But this involves give also the cooking of the files. (Inventions, personal formulas, Greps, etc)
How to resolve this as the PDF does not sound good enough for him?
It is a very good thread to this in
http://aigasf.org/community/legalities/do_you_have_to_give_your_freela nce_client_your_digital_files
but in the legal matter.