Free ebooks are good for marketing purposes - especially for series or debut authors: go for it! We can distribute free ebooks in the most stores (Apple Books, Kobo, Google Play Books, B&N, etc.). Unfortunately, some of the stores may not sell free ebooks or they give a very low price to free ebooks.
PublishDrive encourages free ebooks as part of a marketing campaign for a limited time or as the first book of a series.
However, based on the business model of PublishDrive, we kindly ask publishers that the number of permanently free (permafree) ebooks do not exceed 20% of their whole catalog in case of catalogs over 10 books. We kindly ask publishers with a catalog over 10 books not to keep more than 20% of them permafree at any given period.