This is just a quick tip about the way you can create a downloadable link to some media item from within a rendering variant. Given, that you have a template with a field of type File, and an item of that template has a downloadable resource, let's say PDF. Trying to use that field worn't work normally.
What you should do instead is create a reference variant field to that media item, attached within a File field. And from within a context of that reference variant field, you address to a field called File path. The image below describes that trick in action:
Hope that trick helps!