Open up Norton and go to Settings in the top right corner. Then click on Antivirus and then click on the "Scans And Risks" tab. You should see "Items To Exclude from Auto-protect, SONAR..." If you click on the configure next to these, you can select an entire folder that you can download LCPDFR into without Norton deleting it. (You may also want to exclude it from scans too)
Make sure you only download mods you know are safe into the folders you tell Norton to exclude from Auto-protect, download mods you are not sure about into a separate folder.