Sure, this can be tracked. But the whitepaper needs to exist on a Marketo LP (or a page with Munchkin tracking) so that those that click on the link to the PDF can be tracked. PDF files alone can't be tracked.
Sanford Whiteman has documented an approach where you can provide a direct link to a PDF - but it must exist within the confines of your environment (a hidden landing page to bounce the user off of when linking to the PDF; and accessed by a define set of domains/sub-domains).
Thanks for sharing that article Dan.