Which packaging innovation in the 15th century most dramatically increased access to religious texts and contributed to theological debates during the Reformation?

Throughout history, religious texts have undergone remarkable transformations in how they're packaged and presented to believers. From ancient scrolls to modern digital formats, the way sacred writings are packaged has influenced their accessibility, preservation, and spread across cultures. This trivia question explores a significant packaging innovation that revolutionized how religious texts were distributed and consumed.

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Gutenberg's movable-type printing press allowing mass production of bound Bibles
Illuminated manuscript techniques with gold leaf embellishments
Parchment scrolls replacing clay tablets for durability
Leather-bound codex formats replacing papyrus scrolls