Add Attachment when using Electronic Delivery

SUGGESTED

I know when you select Electronic Delivery when emailing forms such as Purchase Orders and Sales Order, you can click the Electronic Delivery button and add an attachment.  Is there a way to make that attachment permanent so that you don't have to click that button every time?  We have a clients that would like to send W9 forms or Terms and Conditions with the PO that they are emailing.

Thanks

Sue