AutoDesk,the company which created of the famous software AutoCAD is giving it free for the students who use MAC. Most the engineering college students need it to use in their CAD class, so even if they have Windows version in their college and MAC in their rooms they can easily use the AutoCAD software. They have a full version for professionals but for students they have allowed a 3 yr license for the MAC users.
The only drawback of this is that you would have the images watermarked but as long as you are learning the software you won’t care much about it . To have it you need to have a school email address.
Download the software from here .