I haven't done it yet, but the hard-core Certificate of Authenticity guys tell met the best idea is to get a true copy made and have it laminated for shows and whatnot, save the original in pristine shape in case a new copy becomes necessary.
2008 GT/CS: assembled 04-17-2008 delivered 04-17-2009
Odometer today (08-04-2010): 6,507.2
# 2075 of 2509 convertibles # 560 of 718 in Ebony
2009 GT/CS: assembled 05-27-2008 delivered 09-01-2008
Odometer today (08-04-2010): 8,544.2
# 34 of 1705 coupes # 3 of 377 in High Performance White