Literacy in the early Middle Ages was very low, but as I recall, by the time of Reformation quite a lot of commoners could read. Even if they were not very good in reading and writing, by the 17th century many had a copy of the Bible they could read, as well as pamphlets posted on important occasions, etc.

How did they learn to read? Compulsory and state-founded primary education emerged mostly after this period, so who taught the peasants of 15th and 16th centuries how to read?