A urban myth. This from Monticello.org:
“The finished document signed by the delegates to the Continental Congress was engrossed on parchment, which is actually made from animal skin. Thomas Jefferson's original Rough Draft of the Declaration is now in the Jefferson Papers collection at the Library of Congress. According to the Library of Congress,analysis by paper conservators has determined that the paper is mostly likely Dutch in origin. While hemp was commonly used to make paper in Southern Europe during this time, the Dutch were much more likely to use flax or linen rags.”