How to remove "This program is a demo" in the printed invoice?
The only way to remove that from the Garage Organizer's invoice is through a direct purchase of the application. That message is there because you don't have a full license for the application.
But there is one problem and it's related to the acquisition of this software. I tried to locate the official website and it appears there is nothing available which makes it impossible at this time to remove that message even if you wanted to acquire the program.
You can try Home Manage as alternative: http://www.libertystreet.com/Asset-Home-Inventory.htm