If you have created a product on Gumroad and want your customers to be able to take full advantage of the Gumroad app (for iOS and Android!), it is important to be aware of the types of files that can be accessed in the Gumroad app.
For your convenience, we've assembled those filetypes here:
Optimizing a PDF for Mobile:
Some customers would rather download ebooks to their devices instead of using the Gumroad app. For an optimized customer service experience, consider uploading multiple ebook formats. Most importantly, always upload a PDF version, as most devices can easily display them and don’t require third-party software such as .epub or .mobi file formats.
Set the page size to 6x9" and use a 12pt font for the body. Regular PDF defaults tend to make them hard to read on mobile because they are generally optimized for print.