There are 2 things that immediately come to mind in this instance.
The first is, make sure the grain direction of your paper is the same direction as your fold.
It's easy to tell what grain direction your paper is, just fold it in quarters. The fold that has less cracking will be the grain direction. Your fold should always be in line with the grain for best results.
As you mentioned, scoring can help, but the better option here is creasing.
Creasers were developed with digital printing in mind, and there are very affordable manual creasers for digital print available on the market as well as full-blown automatic units.
Hopefully this helps you out a bit.