Should I email a corrected version of my essay to graduate admissions? I realized the writing sample I'd submitted for my grad school application (US grad school) had a small mistake that messed up the formatting of the first page. I'd written the authors' contributions in the footnote of the first page, and because of a small formatting problem, half of it had gone to the footnote on the second page and that half includs important information on authors' contribution. (And since it's a writing sample with multiple authors, authors' contribution should be crucial for the admission committee I guess.)

I've already submitted my application and can't make any changes, but there is still couple of days left till the deadline. Should I send the corrected version to the admissions, explain there was a formatting problem, and ask them to replace the old one with the correct one, or would that do more harm than good?
You can send it. It probably isn't necessary. It probably won't be considered. But it won't hurt. Just include a note of apology for the bad formatting. 

But an error like that should have no effect on your application.