How poor-performing PDFs can affect even your best PDFs
Here's another tip to improve monetization of your PDFs: test different PDFs to see if they return relevant ads before publishing them to your readers. In some cases, irrelevant ads may be returned because the content is too niche and there isn't enough advertiser demand for that category. Or perhaps it may be that the writing style is too varied and the analysis cannot determine the appropriate common keywords. (You can refer to my previous post for more tips on how to improve ad relevancy).
Over time, pricing for each publisher is automatically adjusted based on the performance of their PDFs. Therefore, if you publish a lot of poorly matched PDFs that don't result in clicks, then it can have a negative impact to the monetization of even your well-matched PDFs.
The best analogy is the real estate market. Everyone wants to live in a nice neighborhood. When some leave and depress the prices, that drives others to leave and results in a cascading effect. Likewise, when people are buying in and there is too much demand for the same location, then the prices go sky high. The marketplace team applies this principle of market planning so that all participants are, in the long run, better off in the market.