Soak it in lighter fluid for 5 mins. Then remove, then wash with dishwashing liquid. Then freak out over all of the smudges!! Then more lighter fluid, rub well with a paper towel, then more dishwashing liquid…repeat as necessary, till you get a crystal clear surface. Trust me, you’ll get there.
Soak the paper towel with water when done; spontaneous combustion is a real thing!!
Maybe they used this…
This is my favorite bit of all time. Gilda!
FWIW this is a place where the plastic single-edge razors can be useful.
I have found that one of those citrus sticker remover products works wonders. When the paper is really stuck I spray or pour the liquid on, let it soak for an hour and then pull the paper off. I have used this technique more than once to rescue perfectly good acrylic.
Hi, were you able to get this to work out?
Oops, missed that…
I can’t recommend the lighter fluid / wd-40 enough…works really well, with minimal effort 
+1. Ronson Lighter Fluid works wonders in that area.
Coleman stove fuel is the same stuff and cheaper. You can get it by the gallon.
Of course you always want to try something like this on a small sample. That being said I will probably try using UNDU … it’s a liquid that is fantastic with the use of sticker removal. It’s safe enough that you can pour it over the top of a traditional printed photograph and it will not damage the photograph. It can remove a sticker and still leave the tackiness intact so you can reuse the sticker elsewhere. I also use UNDU to clean up any adhesive left from the sticker. I have used UNDU for probably 10 years on scrapbooking type projects, etc. You can buy it at most places that sell scrapbook supplies (JoAnns or Michaels)…but I am including a link to wal-mart because they have a lot of stores! UNDU
Note: It is not greasy like Goo Gone is.
Kerosene is supposed to work well on acrylic.