Pawel nailed it.
I'd reinforce two of the points.
1. When I was younger, I'd put the decal in a plate of water and wait until I could poke it loose. Bad idea. Now I put it in until I can see that the backing paper has absorbed water, then put it on a piece of paper towel to let it dissolve the glue.
2. Cut up a long decal. The plusses outweigh the minuses.
And...
If you have access to a scanner, make a high res scan of the sheet. It's perfectly legal if it's for yourself.