These kind of brushes are one of my favorite types of brushes for distressing work. Why? Because they're specifically designed for roughening edges and adding fold marks. There's a lot of grunge brushes out there. But this is the only pack specifically made for this purpose that I'm aware of. Download the brushes and then I highly encourage you to watch this tutorial video.
These large Edge & Fold Brushes for Photoshop are perfect for adding rough edges and subtle folds to your work. I highly recommend using them as a layer mask on your work. You can watch a tutorial here. If you like these brushes check out this pack full of similar goodies (included more edge brushes).