You can hide the column in the normal mode by setting its Visible/Display property to false. But all these columns will be appearing in the Edit/Insert mode.
You can refer to the following online demo which provides demonstration on using RadUpload in the EditForm of a RadGrid: Using RadUpload in an Ajaxified Grid
You can also refer to the following help document which explains on how to manipulate files that are uploaded: Manipulating Uploaded Files