I've considered printing the private key portion in invisible ink, which requires a special reader, and doesn't allow the printing party to view the QR code, but even this involves an element of trust in the minting process, and would also require that the private key and QR code is not visible as the paper wallets are generated. Perhaps the only way for someone without Internet access to securely purchase bitcoin is at a BTM that prints a paper wallet as he deposits the cash. But one still has to trust the BTM and those who operate it - or have some type of escrow or reputation trademark.

By way of comparison, many industries - including banking - are overly trusted. It's a double standard. But I will continue my quest for trustless money.