Salesforce doesn’t allow saving .rtf files as native Note records. If you upload an .rtf file, Salesforce treats it as a File record, not a Note. In short, any attachment or file that Salesforce itself allows you to download directly, our app supports downloading as well.
PS: View Mass File Download, Salesforce file download app on Salesforce AppExchange: https://appexchange.salesforce.com/appxListingDetail?listingId=a0N3A00000EcsAOUAZ