In CS6, you could select the artwork, then go the the Artboard Panel, choose options, and then choose "fit to selected artwork" or "fit to artwork bounds." This resized the artboard to fit your artwork. In Illustrator CC, both options are absent in the Artboard Panel and "Custom" isn't there either. I can't find these options anywhere else. Help files assume they are there. I am reopening files in CS6 to do this now. Can't believe they eliminated this feature. I use it everyday. Where did it go?
CS6 Version
CC