Just make sure to sign the original certificate, in INK, then laminate away. All of my certificates are laminated, and I encouraged students to do the same when I was a working CFI. A good friend of mine is a designated pilot examiner and he has taken laminated certificates from many applicants and OKC has never ONCE bounced back the paperwork. And believe me, they will send it back for far less.
Your laminated certificates will last a lot longer.