Found Critical Typo But Not Yet Print and Mail Out; Can I still fix it?

Dear all,

 

I completed my tax return forms and chose to mail it, since I am not eligible for e-filing; however soon after, I found a critical typo in my forms. It has to be fixed.

Now I have not yet printed it out or even mailed it to IRS.

Do I still have chance to edit it? Do I use Amend (change) return function to fix it? Will there be any extra step I need to pay attention to?