Mimeographs are essentially low-cost but low-quality and easy-to-use printing presses. They produced good-enough copies at a cost far lower than hand copying.
Copies are produced from user-created stencils. Mimeographs remained the dominant form of document duplication for almost a century until photocopy machines became inexpensive and ubiquitous.
For decades, mimeographs were the only way to cost-effectively self-publish magazines and short books.
“Within a few years the position of copyist, scribe, or scrivener disappeared,” said Frank Romano, president of the Museum of Printing in Haverhill, Massachusetts.
Edison invented and patented core mimeograph technology. He sold it directly and also licensed it to the A.B. Dick Company of Chicago that trademarked the term “mimeograph.”
This is an odd case where a different company reaped the bulk of the profit from an Edison invention.