POD enterprises abroad can be roughly divided into two categories: ① Focusing on the on-demand printing and distribution of books, mainly serving publishers and helping the latter to order books first and then print them. This kind of representative enterprises, such as Flash Power Company of ingram micro Group, paper book offset printing manufacturer of Bertelsmann Group, American digital printer Vestcom Company, etc. ② Emphasis on publishing on demand, mainly serving authors and representing enterprises such as Xibris, iUniverse, Authorhouse, Lulu, Infinity, etc.