The emails are used for notifications, rather than as a file delivery medium As a general rule, files are downloaded in either the Order control area or the File Manager depending on whether they are sent as part of an Order, or sent via a Form or FTP.
There are two exceptions: Files sent via a Form, or files generated via eDocBuilder templates. Links to files sent via a Form can be delivered via the Form email. See Sites > Email Notifications > Customizing email content above. For eDocBuilder Templates, the production file can be delivered to both you and your customer. However, it does not display a download link (Delivery URL) unless 1) the Product uses an eDocBuilder template and 2) is also marked “Digitally Deliver eDoc File”. See Sites > Products > General: Checkout Option for this product > Digitally Deliver eDoc File.