The Central America-Dominican Republic-United States Free Trade Agreement (CAFTA-DR) provides duty-free trade on most goods traded between the United States, Costa Rica, Dominican Republic, El Salvador, Guatemala, Honduras and Nicaragua. My last article provides some background about the agreement.
In order to get this preferential treatment, the importer is responsible for making the claim. The exact manner for doing so is determined by the individual signatory countries. While there is no specific certificate of origin form that must be used (unlike NAFTA), there is a commonly used version of the CAFTA-DR Certificate of Origin form, which you can download here.