muzza64 - 5:29 pm on Sep 5, 2012 (gmt 0)
My view on the Panda effect is (or was!) that Google hits the sections of the site that are low quality or are close to the low quality stuff. Your worst hit sections are several clicks away from the PDF's by the sound of it (before and after re-locating them to a subdomain), so not very close really.
The changes you made to the worst hit sections sound too minor and too recent to be the reason for the recovery (but could be nevertheless).
My personal view on the subdomain solution is that if the low quality content is simply moved to a subdomain with no other changes and is just as accessible after moving it to a subdomain as before, it doesn't really change anything from the user's perspective so I wouldn't personally expect it to be a long term Panda solution.
There have been examples of sites temporarily recovering after moving content to subdomains, but only temporarily so it will be interesting to see if the recovery continues/sticks. I hope it does for your sake.....but it will blow much of my understanding of Panda out of the water!