What makes Colin a really interesting signing is that he suddenly started to score goals last year - lots of them. He led the AHL in goals with 42 last season. In two previous seasons in the AHL, he managed 22 goals in total.
McDonald also has good size (6'3").
The Pens had someone that profiled in a similar fashion - Tim Wallace. Though Wallace never reached the 40 goal mark, and doesn't have McDonald's size, he did jump to 27 goals two seasons back. Unfortunately that didn't translate to any prolonged NHL playing time (or success).
If McDonald really has started to figure it out, it's not too late for him to contribute at the NHL level, but at the age of 26, he's going to need to take advantage of any chances he gets with the big club.
Given the Pens' need for size and scoring from the wings, this was a great move by Ray Shero.