Yes! We're using PledgeManager to handle post-campaign pledges. It'll let you pay your shipping costs and buy extra add ons, and let you pick what add ons you want with money you added to your pledge on Kickstarter.
The game draft PDF is in update #1 (https://www.kickstarter.com/projects/1549920133/legacy-life-among-the-ruins-2nd-edition/posts/1946180) while playbooks and handouts are in update #11 (https://www.kickstarter.com/projects/1549920133/legacy-life-among-the-ruins-2nd-edition/posts/1949796)
Don't see the answer to your question? Ask the project creator directly.