If there's a PC link to the updated version you don't need the Mac one.
Download the pc version unzip it take the game folder and drag it in the Autorun folder of the Mac version (holding the alt key) release it and when a pop up window will appear click merge and you'll have an updated version.
The path to find the Autorun folder is: right click on the game icon and click Show Package Contents (in the windows that appear)/Contents/Resources/Autorun.
Just do a backup of the older game folder (inside the autorun folder) for security and you're done.
P.S.Release on to the autorun folder and not on the game folder or else you will be asked to replace the file and sometimes this could lead to a broken game, if you release on the autorun you will merge the files and the update will work, I use a Mac as well so I tested this solution and it works fine.