If a man signs a child’s birth certificate is that the same as establishing paternity? Or is it two separate things when filing for custody in Fl?

  For legal purposes, you need to have paternity established through the Courts, even if you are on the birth certificate.  You can file a Petition To Establish paternity  and, in the same court proceeding also set up a parenting plan and timesharing agreement.  Child support will also be established at that time.       You can find the form to establish paternity by doing a search of "Florida Family Law Forms- Establishment of Paternity.   Best of luck, Cindy Vova Law Offices of Cindy S. Vova Broward/Boca Raton 954-316-3496/561-962-2785