FPM Keys for Mac users can be found in "/usr/local/share/foxit/Foxit PDF Editor/Licenses/ "
Make sure you have "view hidden items" turned on. You can do this by opening your Macintosh HD in your Finder and press Command + Shift + .(period).
This will make hidden files and folders appear if you have permissions to on your Mac. You will now see the usr folder appear within the Finder view.