The vast majority of them. Photoshop was designed from the beginning to work with print media -- it's called Photoshop for a reason.
Conversely, the people who just need to whip up some graphics don't need Photoshop; they have cheap alternatives like PaintShopPro, Paint.NET, or competing lesser-known commercial software.
They are in no way, shape, or form, ready for the print production environment. Not even close.