You could, but then there would be a delay in your order's production! (and there is a cost associated with us handling the files for you - currently $49.00)
The best way to handle this is to log into My Account and click on the link to Complete your project or Approve/Reject your proofs.
When you reject a proof with new files, you'll be able to upload them immediately after.
See also: https://support.discmakers.com/hc/en-us/articles/209957457-How-do-I-approve-or-reject-my-proofs-