If you enable “Attach PDF to Email notifications” option, and create an e-mail notification, then you will receive PDF files to your mailbox. You won’t need to insert download shortcode to On-Submit message text boxes or into the email message. It just works.
But first, let’s make sure the pdf shortcut is setup correctly by making it work in the OnSubmit…
Can you provide temporary admin access to your server? support(at)formidablepro2pdf.com
If not, please send a screenshot of the plugin screen with the layout and dataset selected.