Including free files in a Pre-Order
Oftentimes a pre-order will contain a few preview files or (as the kids are calling them) "grat tracks," as an incentive to buyers. To offer free files in a pre-order, you will have to create a regular product on Gumroad - a pre-order in name only.
Here's how you would accomplish this devilish little trick:
Create a regular product that consists entirely of the preview files. In the title and/or description of the product, make sure to include the date of the final release.
Publish your "sneaky" pre-order and start making sales. Now wait...
On the designated "release" date, upload the completed product.
Now go to the Customers tab, Filter by product, and send out a message to your customers letting them know that their order has arrived. They will be sent a link to the now completed product.