The best way to do this is to upload the file, report, or other information to your website and link to it from your Final Welcome email in the signup form design area.
To do so follow these steps:
- Go to your Lists Tab.

- Click on the forms link > design it.
- Select Final Welcome Email from the forms & response emails drop down box on the left hand side.

- Click on the content editing area. (Default text says "Your subscription to our list has been confirmed").

- Type in the text that you want your recipient to click on (like "Get the Report" "Download goes here", etc).
- Highlight that bit of text.
- On the Content Editor toolbar, choose the link icon (looks like a chain link).

- In the popup box that appears, paste in the URL/website address you want your recipient to go to.

- Click ok and your link is set!