From the looks of it all he did was soak the pages in water let them dry and then put them back in the book.
The way he soaks the pages though reminds of how one develops photographs. I took 照片 journalism for a 年 and some the tools he's using look similar to the ones we used. So maybe wetting the book pages will cause something to 'develop' on them at some point?
Or... if he used the water from the Well that brings back 迷失 things, the pages Henry tore out about Emma that we saw her burn, will return to the book. If that's true and Regina sees those pages Emma could be in trouble if that happens.