The thing you got in your AP newsletter was a discount to get 50% off Photo Pass pictures you'd want to buy after your trip. The Photo Pass itself will be given to you at the parks when you have your first picture taken. And then you can use the same one over and over, just hand it to the CM.
We are going in Oct, and I'm wondering if it's worth it to search for the last AP newsletter. BTW, when did you receive the newsletter with the discount? I don't recall when I got the last one either....