I have followed the tutorial videos & searched the BSS forum and can find no way to link to a file. I am trying to link to a .pdf file and there is no function that allows for this. It appears that links are limited to URLs only.
Even your PDF will have a URL, because you’ll need to host it somewhere (probably).
You can’t include a PDF in a Bootstrap Studio project, but that’s a different issue. Upload your PDF to your server, then use its URL as your Bootstrap Studio link.