Can I Upload a Scanned Document into My Submissions?

If you are mentioning about adding a scanned document to your existent submission, it is possible with hidden "Upload" field. By doing this, users don't see that field, so you can edit their submissions after they submitted.

To make the "Upload" field hidden,

After you set the field and the user submitted, you can edit those submissions by following steps from the below:

For further assistance, please do let us know.

Thanks.