CADD
CADD stands for Computer Aided Drafting and Design. It's pretty much a 2-year course that teaches you how to use MS Paint, as of the 2 years Chris has only produced 2 pieces of work (while one might assume they were two big projects over a long amount of time, the two pieces of work he produced were a map of his mall and an incredibly large 3D Mayor's Office about the size of a football field with nothing much inside it).
Chris has two degrees certificates in CADD. Looking at his current art, he'd probably have been better off spending his tuition fees on Lego. The Associate's Degree in CADD is no longer offered by Piedmont Virginia Community College.[1]
Chris states in his phone call to Kacey's father that he entered into the CADD programme without knowing what kind of jobs such a certificate could get him. Throughout his years at PVCC, and in the 3 years since graduating, he still hasn't bothered to figure it out. If Bob and Barbara still cared about anything, they'd be kicking themselves for wasting money on his tuition.
Timewarp
In Sonichu 5, Christian claims he got his CADD degree in May 2006. He had, however, already been suspended from PVCC for over a year by then, so chances are large they just gave him the certificate to shut him up, and to stop Bob Chandler from suing them for playing kick the autistic. If this is true, it could mean that Chris never even finished his CADD classes.
Usage in the comics
Chris's CADD degrees apparently come into use within his comics, he even alludes to them assisting him at many points in his comic; for example, Sonichu & Roeschu's benefit house. However the few basic measuring skills he may have picked up from his CADD courses are made even more pitiful by the fact he never uses a ruler nor are his drawings to scale, defeating the purpose of even learning CADD courses in the first place.
A villain by the name of CADD Chef appears in the comics, mocking Chris's designs for his mall. It is speculated that CADD Chef may be based on Chris's real life CADD teacher, and that he probably gave Chris a bad grade on his real life mall designs. This "injustice" guaranteed CADD Chef a place in the Private Villa of Corrupted Citizens as one of Mary Lee Walsh's minions.