Spaces allows digital downloads for files that aren't larger than 300 MB. To sell larger files, or to have more control over the download process, use Zapier.
With Zapier you can create Zaps, which you can use to send your customers externally-hosted digital downloads when they purchase a digital product from your Space.
For example, you can create Zap for digital delivery by uploading your product to a hosting service like Dropbox or Amazon S3, and then using Zapier to automatically email that file every time a certain product is sold on Spaces. This guide from Zapier covers the basics of this process.