Law in Australia suggests I can be charged with 'theft by finding' if I don't make a reasonable attempt to identify the owner. This seems to be impossible in this instance...
You can start by posting the address here, so Google index it and the owner can respond here. Be prepared to get messages from people claiming to be the owner, so they'd need to provide evidence. And that's the tricky part: even a signed message from the address that funded the wallet doesn't necessarily mean it's the ownerr (it could be the guy who sold the Bitcoins to the current owner).
Another way to get the owners attention could be by leaving small hints by sending dust to the address and in the same transaction send dust those 2 addresses:
1PaperWaLLetFound1xxxxxxxxy1KHknm
1Topic54o8263onBitcointaLkxyvdAVg
(Note: I used Proof of Burn to create those addresses. DO NOT send anything valuable to those addresses, it will be lost forever).The owner will have to know his address, but if he knows it and the wallet was indeed stolen, it's not unlikely they'll check a block explorer to see if the funds were moved. When they do, they'll see the new transaction with hints.
it's probably best that you don't post the public address in public either.
I'm in doubt: there's a privacy concern, but it's not easternklaas's privacy, and I don't think you can say you made "a resonable attempt" at finding the owner without publishing the address.
IF the legit owner still has a copy of the Private Key of the paper wallet, (s)he can easily prove ownership by signing a message with the particular Private Key.
IF they still have the private key, they should just move the funds the moment they realize a copy is missing.