You need an invitation letter if visit China for the first time, but if you cannot provide it, please provide a visa recommendation letter from your company. other additional documents may required are bank statements, round-trip air ticket or hotel booking,etc.

Yes, if you want to come to China holding a tourist visa,it is not nececcessary to provide an invitation letter. But if you have friends or relatives in China, the can give you an invitation letter, which will be very helpful. docauments: bank certificate, round-trip ticket, one white photo in 2 inch ,hotel reservation in China, original passport.
I am a visa agent in China, questions about visa, you can consult me.