[h=1][FONT=arial, helvetica, sans-serif]Bi Sheng 1041 - 1048 (Wiki) invented movable type in China but it stayed local . . . Guttenberg 1468 invented it & the Press in Europe from where it grew throughout the modern world - but for todays world .. . the team that developed Postscript . . . [/FONT][/h]
I have to add two names (breaking the rules): Charles Fenerty and most assuredly Friedrich Gottlob Keller. If you don't know who they are, you should... they burst the one greatest wall that printers faced in making printed matter available to the masses. God bless 'em both: the poor were finally able to buy books and newspapers and still feed their families.
Personally I think the question "Who was the Greatest Person in History of Printing?" is spurious if not down right silly. Unless D Ink Man has some kind of Zen-like twist in mind (which I doubt).