When you buy pre-order, you are purchasing a unique code, to be redeemed against all the photos of a singular person/race number for a specific event (e.g. 'Joe Bloggs' or bib number '1376').
You can also order for a friend. To order more than one bundle, simply select the amount of bundles you require on the event home page.
Once you've purchased, look out for an email which will contain the number of unique codes that you have purchased - each of these are redeemable against all the photos of a singular person/race number. When photos are live, simply redeem your codes. Note: You can only redeem codes for the same event you purchased for (i.e. Manchester Marathon).