You can buy it after when you see your pictures and decide how many you want to buy. At $15 each for individual downloads, if you want more than 11of them it's more cost-effective to buy memory maker. If you think you'll be likely to get it, you'll save $20 by buying it in advance of your trip instead. When buying in advance, be sure to buy at least 3 days prior to your trip, as there is a 3 day wait before MM kicks in and the first pictures start being included st the discounted price.