The USPTO announced on June 30, 2009, that the World Intellectual Property Office (WIPO) became the fourth country to participate in the Priority Document Exchange Program (PDX).  This allows patent applicants to exchange electronic priority documents between the USPTO and WIPO at no cost to them.  In addition, the USPTO may electronically exchange non-participating priority documents between the Japanese Patent Office and the European Patent Office via a corresponding JPO or EPO application file wrapper.                

— USPTO Commerce Alert dated June 30, 2009