Although it's been on the market for years, I still run into people who don't know about "Undu." This magical product is a must-have for every scrapbooker.
Touted as "the original adhesive, sticker, tape and label remover," I can tell you from experience that this product works. I have successfully removed stickers and other embellishments affixed to a scrapbook page - without tearing the sticker or the paper. Repositioning photos after they've already been glued down is no problem; Undu will dry quickly leaving no damage.
The only disadvantage I've discovered are the strong fumes (somewhat like paint thinner). You may want to take it outside to use - otherwise, make sure your room is well-ventilated.
Take a few moments to do some Undu product research of your own, and you will find there are many fans of this practical product.