On October 8th, the State Intellectual Property Office of China (SIPO) and the U.S. Department of Commerce’s United States Patent and Trademark Office (USPTO) launched a new free service of electronic exchanging patent application priority documenrts directly. This service is for thoses applicants who apply for the patent in China or US for the first time.
  Both SIPO and USPTO can benifit from the electronic exchanging service. The service helps reduce offical management cost and applacant’s production costs.  
   You can find more information from USPT website.                                                                                
   http://www.uspto.gov/news/pr/2014/14-28.jsp