Where is Downloadable Content Stored?

[timrsfo]

I added a new downloadble product, a pdf book. I selected the file from the host and it appeared to upload. I did not add link. I can see the product and purchase it but it responds with no link when I download it. It responds the same for other downloadable products. Though it will download samples.

My question: where does this uploaded file go? Can I download it? What would the link be.
Or could I some dual-purpose the nginx container and use it as a static file server?

For my purposes I'm just using this for experimentation, its not going to be a live system
thanks,
Tim