There is nothing stopping me from verbally speaking about the second amendment and the rights of gun owners. However...if was told that I needed to buy a permit in order to do that, I would consider such a thing to be a violation of my right to free speech. Because that is directly related to the exercise of the right.
But a tax such as you are talking about is not applied SPECIFICALLY with my right to speech in mind. In that instance, the tax applied to the buying or printing of the leaflets in merely incidental.
Where would we be today if only Miller had shown up for his court date?