Hello Michael,
There is no specific procedure of switching from Hotel Booking Lite to Pro version. You should simply install and activate the Lite version, and then deactivate the Pro version. All the data and settings (within Hotel Booking Lite functionality) will remain.
Could you let me know why you decided to switch from Pro to Lite version? You will loose some very useful features available in the Pro version after the switch.
Regards,
Andre Flores