I still maintain, in a pinch, go ahead and gently peel 'em out as needed. The full page ones are supposed to be empty underneath (unless they pasted over another country at the time). If you have time, get another passport. If you're a few days away from a trip to Indonesia (notoriously bad about requiring blank pages) and can't get new pages in time, gently pull! I'm sure there are tips on the internet for removing stickers (cold/hot/steam/etc) if you're worried.