::Hi Mark, sorry I wasn’t more specific. From the invoice journal (header or line, depending on whether the attachment was on the sales order header or line), you click on the document handling button in the status bar or you can use the File / Command / Document handling menu option to get to your attachment that got copied over to the invoice. You should then be able to change the Internal value to External and reprint the invoice to get what you wanted.
If you’re not able to edit the record, you might want to add the invoice journal / invoice lines tables to the active document tables to allow editing at all times. If that’s the case, let me know and I’ll tell you how.