How to optimize PDF files for SEO?
Google indexes all PDF, doc and other text files. Sites like Scribd.com docstoc.com are highly authoritative and if you put your same blog content in those sites, chances are high they outrank your blog post. So when you publish PDf docs, spin them or change titles atleast.
These kind of docs should be targeted for long tail and referral traffic and should not compete your target keyword.
Here’s a different question Matt answers w.r.t PDf docs