This is a great question! For too long, Anglo historiography concerning the Reformation has been dominated by a sort of anti-Catholic narrative that saw the Middle Ages as a time of corruption and ignorance. The Bible, we're told, was kept far away from the people - indeed, it was chained to the altar in the Church! The latter fact is true, but is true for a different reason than people think: prior to the advent of the printing press, it was massively expensive to hand copy a Bible. Few could afford to have their own. Hans Hillerbrand reminds us not to be blinded by the declension narratives too often surrounding late Medieval Europe: "The picture of a church in a state of complete perversion on the eve of the Reformation has little historical basis. Nor is it correct to say that in the early sixteenth century every sensible person yearned for ecclesiastical reform." (The Protestant Reformation, xiii).

So, how much did people know of the Bible prior to the printing press? Late Medieval and early modern culture was absolutely saturated with the Bible. I can speak specifically to Germany. While there are claims that in Germany, for instance, no German Bible existed prior to Luther, this has been discredited over and again (cf. Thomas Kaufmann, "Vorreformatorische Laienbibel und reformatorisches Evangelium," Zeitschrift für Theologie und Kirche 101 (2004): 138-174, who catalogues German Bibles prior to Luther's own translation). Bibles were found not only in churches, but city libraries. Nuremberg City Library had a complete Bible in the 1420s, according to Andrew Colin Gow, "Challenging the Protestant Paradigm. Bible Reading in Lay and Urban Contexts of the Later Middle Ages," in Thomas Heffernan and Thomas E. Burman (eds), Scripture and Pluralism. Reading the Bible in the Religiously Plural Worlds of the Middle Ages and the Renaissance (Leiden: Brill, 2006): 161-191.

The translations done were of varying quality - but most important is that there were many vernacular, low German translations in existence prior to the Reformation. The people who were using these would not have been the academics (not primarily), but laypeople (cf. Falk, Die Bibel am Ausgange des Mittelalters).