Fallout 3 booth pretty much won the "Oooooooh!" contest at PAX by about a million rads. Not only did they have an Airstream trailer, fully kitted out in 1950s style and with Fallout 3 goodies inside, but they also had some of the best schwag at the expo. Vault Boy Puppet? Yes, please. Fallout 3 Penny Arcade poster? Don't mind if we do. The Vault Dweller's Survival Guide, Pocket Reference Edition? Oh my stars and garters.
In the gallery below you can check out the entire guide that they were handing out at the show, and it may very well be the actual game manual. You get 50 pages chock full of tips for surviving in the wastelands, info on the different weapons, details about the creatures you'll encounter, and tips from Vault Boy himself. It even has a map and notes section in the back for your own enjoyment and doodling.
Of course, the best advice can be found on Page 39: "Are you in immediate danger? You are beyond help. Drop this book and run." Update: Download it as a PDF!