Set up your 'Export Document' workflow action as normal by choosing the export file type and creating an email using the 'download.uri' variable, as shown.

At the bottom of the list of email variables, there is a variable called 'Download Expire Date'. You should insert this into an appropriate area of the email body text.

This will become the download expiry date for the generated file, i.e., 7 days from when this action is called and the file is generated.

All you need to do now is enter a recipient (if you have not already done so) and save your 'document export' action settings.

When this action is called, an email will be sent to the recipient containing both:

1. the download link for the generated file (in this case, a PDF)
2. the expiry date of this download link