To those, who recommended "Elements of Magic" - please refer to "Elements of Magic Revised", because the original PDF is still available for sale (unless you really mean the original version and then I would heavily disagree with you

).
On topic: Most PDFs, I'd recommend, are already mentioned.
Poison Craft - Everything, you wanted to know about poisons
Unlikely Heroes - NPC classes upped for player use
A Magical Society: Medievil Europe (?) - what, if magic would have been real in medievil times? There's the answer!
A Magical Society: Ecology and Culture - If you want to build a campaign world, read it beforehand.
Unorthodox Classes - Actually one PDF for every class. Alternative core classes, superb quality.
Libem Liborium - everything you need for book writing
in character
A Dozen ... - a lot of PDFs for the uppolishing of the campaign. A lot a things for the flavor.
Buy My Snake Oil - and others from Top Faction Games. Like the Dozen-books from RoninArts.
That should be enough, shouldn't it?
