So it seems I goofed, I got my Digital Collector's Edition bakcr thingy, but forgot to add teh expansion download and teh alamnac. Is it possible to add those tow later wihtout having to pledge anew?

So it seems you goofed twice - we are already discussing this issue:

 

http://forums.obsidian.net/topic/64751-cant-ever-get-addons-in-the-future/

Ah, I see, thank you for sharing !