Popular DLCs as Black Ops II have two PKG file :
The first that includes the new files on the PKG that will be placed in the directory of game,
and the second that applies the fixed edats for make the DLC working well.. (usually called DLC Fix)
Then this is useful for avatars or for very rare DLCs that aren't shared by community ( for example, Ace Combat Assault Horizon special aircrafts, I can't find them ),
For example, if someone buy this DLC, he should find the files that the DLC added and make a PKG, and then find the edat, and fix it by converting the rif to rap and blablabla. Then the DLC is ready for all

In the most of cases as I said before, for DLCs they make a 2nd PKG that includes the edats files