It depends on how you're going to use it. When I made wafer paper leaves, I brushed them lightly with piping gel like the directions said. Left them for over a week and they never dried...just got sticky and even stuck to the rack I was drying them on. I'll never do that again. Piping gel can be used as a sort of glue though if you need it. I wouldn't wet wafer paper directly unless you need to form it or something.
I've tried printing on wafer paper and it always looked awful. I use frosting sheets instead which are better on cakes anyway cause they soak into the icing. Wafer paper is great with edible ink markers though. You can kind of use it like tracing paper because it's transparent.
**Please don't buy the Edible Imaging packages that are already put together for you. They are way overpriced. $209 is too much. You don't need any special programs that you can't get for free and wafer paper costs so little and produces really poor quality images. Buy your iP3000 printer separately(I've heard of others getting them new for $20-$30) and then buy your ink and frosting sheets from somewhere like www.kopykake.com