To get started, navigate to the campaign where you'd like to view and download old reports. Then, click Reports in the sidebar on the left.

Next, click the name of the old report you'd like to view or download.

This will open up the report editor. Then, at the top, click Activity to open the activity logs.

In the "Emails" tab, you'll see a "..." button for each time the report was automatically generated and sent. Click "..." and hit the "Download" to download a PDF copy of the report.