No, you can only add supporting documents to an application when it is in draft form. All supporting documents must be attached in order to submit. As soon as it is submitted, it is given to the scholarship provider to review, and therefore no edits or additional attachments can be made.
If your financial aid offer wasn't enough to cover your bill, we recommend you submit an appeal. Learn more about financial aid appeals here.
If you'll need a student loan to cover the rest, begin by researching the lender that will give you the best rate. Most private lenders allow you to answer a few questions risk-free and then get your estimated interest rate. You’re under no obligation to actually get the loan. We recommend checking with Earnest first. Get your rate estimate from Earnest here.