The third and least used among the 3 formats is the PDF eZine. Publishing your eZine in PDF format can consume a lot of time and effort on your part but often make up in quality readership
Due to the commitment, PDF eZines are usually published on a monthly basis. The great part, though, is that you can put in your affiliate links in your PDF eZine issue and allow your subscribers to pass the eZine issue around.
Given the choices, however, you do not have to necessarily choose strictly one eZine format, as some eZine publishers today do publish in more than one format.