DC is automatically added free whenever you print through Paypal.
Whenever someone says a lot of packages are suddenly going missing, I suspect there's a local issue--the PO you drop them off at, the local distribution center, that sort of thing.
Did you have DC on previous packages? You should be able to see some info on where they stopped showing progress. Even though DC isn't really tracking, at least some packages usually have some location data along the way.
I'd report missing packages to the postal inspectors--sort of the police of USPS. If there are more reports of missing packages, they will investigate:
Missing package? Package missing its contents?
http://www.gotogreatpanes.com/blog/2008/02/08/missing-package-package-missing-its-contents