RE: We do need it to print, but not something that goes in the "Customer Message" area, because it's a dropdown list of messages you can make and choose from, not a text box.

Right. OK, needs to print and not from a pick list.

RE: We would need potentially each message to be different, reference each specific job the estimates are for.

Why not use the Description column on the Invoice/Estimate table? Seems the perfect solution based on the needs you've stated...