It's not part of the artwork and doesn't seem to be hurting anything, but I get this on a lot of client logos and I'm wondering how to get rid of it.
I think it's part of the artboard, but can't find anything to select/change/remove it.
It's the print tiling indicator, basically showing you what and where your artwork will print with the print page size you currently have set.
You can turn it on and off from the view menu (View â†’ Hide/Show Print Tiling).
You can even move it around manually with the Print Tiling tool, but unless you're directly printing from Illustrator there's usually not much use for it.