Create a product for the download in the normal way at admin/products.
Give it an image, price, quantity (if appropriate) etc.
First of all go into the app store, and add the free Shopify Digital Downloads app (it is free, so you shouldn’t need to be the account owner to do this).
Then you can go back in to the product , click into it, and click on the […] box in the top corner and select ‘add digital attachment’.

Add the epub etc file:

Here's what it means and what to do.
This is a stellar example of what happens when you consistently show up and put your genuine self into your content.
Writers and journalists are always looking for authentic voices, and if you're publishing regularly, you're infinitely easier to find. Read how Chris did it.
From June 3 2026, Shopify is making some small changes to the information it asks your customers for when they check out. Nothing big, but it's worth knowing about so there are no surprises.