The pdf add-ons can be added to any pledge tier.
The physical add-ons require a physical content pledge tier to be added. (e.g. printed copy of core book)
This is how you add an add-on to your Kickstarter pledge:
1) Go to the BLACK VOID RPG Kickstarter page and press the "manage your pledge" button. If you have not pledged yet it will say "Back this Project".
2) Increase your pledge in the Pledge Amount box by the total of the add-ons you want to add.
3) Do not change the tier you are currently pledged at. Changing your tier might cause you to lose early adopter exclusive rewards or other rewards, so be 100% sure before changing the tier and keep in mind that you will need to add the total of your add-ons onto the amount of the new tier you chose.
At the end of the Kickstarter campaign you will receive a survey that will ask you questions so that you can explain how you would like your add-on money assigned.
NOTE: All physical add-ons require a physical content pledge tier to be accessible. If physical add-ons require additional shipping fees you will be made aware of it prior to shipping.