You can add additional copies to your pledge by increasing your pledge amount by €35 per Initiate copy or €49 per Master copy. The same applies to Ambassador Packs - you can add one Ambassador Pack per each copy of the game by increasing your pledge by €5. You can also do this later in the Pledge Manager.
Backers outside of EU and US are limited to at most one additional copy or using the group pledge option (i.e. pledge for 1, 2, 5 or 10 copies of the game).
If you want to pledge for more than two copies please check the ‘Group Pledges’ section on the campaign page.