Link to a file field in the body text? I have a content type that has a file field. I would like the body field to be able to link to the file. E.g. "Our research (PDF download) shows..." with the link becoming the download path for the file.

I can see the challenge: the path may not even exist at the time of creating the content. Is this something the token module can help with?
Not 100% exactly what you're asking for, but it may solve your requirement:

The IMCE module allows you to upload documents (and images) and integrates them in the body text. You don't need a separate file field if all you need is a document integrated into your text via a link.