Hello!
It is copy of my mail to support, but I was told to post this on forums!
Long time ago, before release of Borderlands 1, there was pre-order bonus for the game. It was Mercenary Weapons Pack DLC. This DLC was for Xbox 360 and PS3 versions of the game. It was never officialy avaliable on PC.
Now, some people find out that this DLC actually is in the PC version of the game but it is locked. Strangely, Xbox One version of the game got this feature after realase of the game and now it is perfectly avaliable for all users (even to those who did not pre-order) of Xbox One version of backwards BL1. For PC version, it only takes to add two short line of plain text in .ini files to unlock this DLC. This is applied to Original and Enhanced versions alike.
Is there any chance that Gearbox can update games to unlock this DLC for everyone (maybe only for Enhanced edition)?