I should really know more about printing than I do. I know a very little bit but then I was never too interested in those aspects of writing and visual arts, I was more interested in the act of creation itself. There has also been a push in recent years to accept things posted online as being "in print." I disagree with this because it is antithetical to the entire medium but it seems this concept is gaining momentum (because it is being pushed by all the wrong people for all the wrong reasons but there it is). Still, those in the printing business have needs and there are sources to provide them. Check the link above for more information.