The printing press wouldn’t have led to the spread of literacy without another crucial factor: underwear. From The Guardian:
Rags from discarded pants and knickers led to a 13th century breakthrough in the making of cheap paper, undercutting expensive parchment.
Research into fashion habits has shown that the use of underwear increased dramatically after 1200, both on the continent and in England, as more people moved into towns. The International Medieval Congress heard yesterday that the rural habit of wearing nothing under a rough smock or leggings was frowned on as peasants developed into tradesmen and found themselves running shops with customers of the opposite sex.
Paper could be made cheaply from rags; a few sheets of parchment required killing a sheep and curing its hide.