Just to mention I brought the game and I love it however on mac I can't seem to download the ending/achievement guide <3
Okay, I just figured it out...
Click on the 'Buy Now' as if you're going to purchase the game again. Next the link saying 'I already own this' or something to that effect. Then put in your email for the previous purchase link to be opened for you. The updated ending/achievement guide will be there for you.