Putting out a newspaper, or at the very least a leaflet is not all that difficult. Historically anybody who could learn the tools and afford to buy them could do it independently. Although more commonly an individual would pay a printer to put out whatever it is he (and often it was a man) wanted to publish.
This trend continued, presses were big and complicated but eventually, like all technology they got smaller. Smaller presses accompanied by an easier process meant that putting out a flyer or a leaflet became easy. So easy in fact even a horse could do it.