[bumfluff]

I'd imagine it'd show as a direct request if it came from something like a .pdf document. There's no referring site. I don't see how it would have any effect on search engines, as there's no search engine involvement. As for value, I guess that depends on how your site makes money (ads or product/service) and the document itself.. if the document is about a field related to your work, then the viewer probably already has some interest in what you do.