Good Idea. I think the PDF signing is overkill, but Good Idea.
Here's a bitcoin business I want somebody to create and run: "Coin on a Stick"
You sell USB sticks containing Mac and Windows versions of the latest bitcoin (including the entire block chain) plus a wallet file containing N bitcoins.
Sell them via Ebay or PayPal, and ship them ONLY to a PayPal-verified address.
The buyer has to trust you not to double-spend the coins in the wallet, and has to wait for delivery of the physical USB stick. But they don't have to download or install anything (they should be able to just run bitcoin from the stick and transfer the coins to themselves or a mybitcoin or mtgox account).
But, since you are sending a physical product to a verified address, you'll be treated as any other merchant selling real goods by PayPal or the credit card companies.