Hmm...wonder if these are the same companion tickets that you will have to redeem through companionbooking.com. I received 2 of these a few months ago on a similar offer after I subscribed to Travel and Leisure. The companion booking vouchers are based upon booking travel through companionbooking.com and the price for the ticket that you have to purchase to use the "free" companion ticket are usually higher than what you would pay for two tickets through the airline's website.

There are numerous web articles about these companion tickets that deride them as basically a scam.