I would suggest purchasing his ticket online, and getting an e-ticket. I'm not sure exactly if they have etickets available for that location - but it would be your easiest route. That way he just needs to print it out and have his ID ready - no complicated issues with mail and all that.
Are you using Air Canada for the entire flight, or just while he is in Canada? becuase I would suggest using a different airline. Air Canada has recently changed thier baggage limit to 1 checked 23 kg item, an extra bag is $40, and more after that I think $150, and if any of his luggage is just the slightest overweight, they charge $100 per bag.
West jet on the other hand allows 2 pcs and only charges $40/overweight bag, and not to mention they are very friendly. I found Air Canada to be just grumpy overall.
I know things are getting ridiculous with the airlines, with weight restrictions and raised prices. He can't land in the U.S. at this point, I refuse to pay them for a visitor's visa for a 4 hour layover. Right now I see some not bad flights on Air Canada, Lima to Toronto, Toronto to Calgary. I will certainly look into LAN via Mexico City. I am just wondering where it is he will "land" for immigration and what the best price would be too. Since you have all confirmed it is possible for me to initiate it on this end, I will make a call to whichever airline I choose and just confirm the steps with them. THANKS