Sometimes you may find a fix like KB2975071 that has been released for both AX2012 R2 and AX2012 R3.
The issue is the Download button is only available for AX2012 R2, but not for AX2012 R3.
The hotfix process of the In-Market Engineering team is that they release a fix for the customer that reported the problem for their version. Then they port the fix into the future versions and it will become available in the next cumulative update for those versions. In order to download and install the individual hotfix other customers should be able to use Update Installer on LCS or download a latest cumulative update and chose Advanced Installation option.