This will allow you to set comments on pages and posts on a per case basis. Follow the instructions below:

Inside of your dashboard go to the post you want to allow comments on...

Once the post is open go here.. This will be at the top right of your screen

Next select this...

Once that is done you should find the option to set comments below..

and we are done!

I do suggest not ticking trackbacks... they are annoying and have very little relevance.