When adding a pre-order product, you can include a few free, preview files as an incentive to buyers to order early. To do so, you will have to create a regular Gumroad product (a pre-order product in name only).
Add a product by going to your Products dashboard and clicking New product. Select a Digital or Physical product, and then click Classic or Product (Start selling today).
Name your product, add a price, and then click Next: Customize. To upload your files, scroll down to Content and upload the free files you’d like to include in your pre-order. In the title and/or description of the product, be sure to include your product’s release date. Add a cover image, update your settings, and publish when you’re ready.
On the day of release, simply click on your product in your Products dashboard and upload the completed product files.
To let your customers know that the product has been released, go to your Posts dashboard and click New Post. Under Audience, select Customers only and select the name of your product from the Bought dropdown menu. Type your message in the corresponding box. They will be sent a link to your now-updated product!