My best guess is that you want a larger margin, as oposed to a border. While technically, you can increase the page size so that you can have a larger maring in which to put annotations, it's a huge pain and not adviseable.
Instead, why not use sticky notes? They don't take up any space and you can type as. much feedback as you want right in the sticky note.
Does your document have to be in this layout? You want want to consider changing the layout to a single column, maybe more toward the center of the spread. That way, you'll have a bigger margin to work with.
What kind of class is this for? Is it an Acrobat class? If so, we can walk you through the process of actually changing the page size in Acrobat. But it's convoluted and I don't reccomend it. Even people who work in Acrobat professionally every single day struggle with accomplishing this.
I'm hoping you have the freedom to change the kayout in whatever publishing program you're using. as opposed to trying to change the layout in Acrobat. Assuming that you do indeed, have the freedom to change the layout, what publising program are you using?