<p>Right below the personal statement, theres an option to upload a document containing additional information. What kind of additional information do they mean? An extra essay?</p>
<p>Could be anything you feel would strengthen your application. Some people need to submit a letter explaining unusual circumstances that have impacted their applications. Some people who feel that their ECs aren't well-represented on the application submit supplementary materials - for example, you could send a resume if you didn't have room for everything on the application (!), or if you're an extraordinary poet you could send samples of your writing.</p>
<p>Of course, none of this is necessary - the majority of applicants don't submit extra information, and it won't hurt your application if you don't. It's just an option in case you want to clarify or enhance a certain aspect of your application.</p>