Some (... may be more ... <img src="images/graemlins/blush.gif" alt="" />) years ago, when playing with electronics and etching my own printed circuits, I used to protect them with an aerosol, which deposited some kind of plastic coating.
I also used this method to somewhat "waterproof" papers.
But I guess waterproofing the paper won't do anything about its deteriorability (did I just invent a new word or what ???? <img src="images/graemlins/grin.gif" alt="" />).


Regards.

Alain