In that case, is PDF traffic really the kind of traffic you want? You'd probably be better off just promoting your site within the PDF, something like, "Download more great sheet music at www.example.com."
That way, you get the exposure no matter how it's spread, whether someone shares the PDF or a printed pile of paper with friends.
Also remember that some people might have browsers configured to automatically download PDF files, instead of opening them. So if someone directly linked to one, adding a link inside the PDF might at least get them to visit your site if they want to check out other songs.
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