uhh alot of the times pros who have stickers on there skis the stickers get scratched off but they have so many that they can just put more on. theres not really any other way that im aware of.
you could do a coat or 2 of urethane on them.. but make sure its something you want permanently.. also if your skis are matte (not glossy) use a non gloss clear urethane (non water based)