The voucher you bring to the park looks like a rectangle coupon. (mine was taped to the front of the case. The code for the CD is in the inserts of the CD case. Mine was in the folded insert, printed in the literature. Unfold the insert and you should see it.
When I exchanged the voucher at the Main Street Photo store, I actually received an entire PP Plus package, which included the lanyard w/PP+ card, the stock CD, and another code for the PP CD in the CD insert.