Note: This procedure involves editing a game file; create a backup copy of the file before proceeding.
Use a text editor to edit the “WillowDLC.ini” file in the “\Steam\steamapps\common\Borderlands 2\DLC\POPremierClub\Lic” folder.
Locate the following lines and update them to match how they are listed below to unlock all promo items:
[PromotionalUnlocks]
+UnlockId=1
+UnlockId=2
+UnlockId=3
+UnlockId=4
отсюда