IanTurner - 9:10 am on Sep 14, 2012 (gmt 0)
I don't think that having the PDFs on another domain would be an issue - especially if it was a subdomain of the original domain, this is done by many large companies to improve performance of the site.
If your local server delivers the PDFs slowly there might be an issue with the ranking of the documents themselves which could be improved by putting them on a faster connection.
Why do you have a nofollow on the links? If you know the PDF content is good then there is no reason to have the nofollow in the links.