When receiving the registration key for the Invoice template, you will also recieve the passwrod to unprotect the sheets and make customizations as you wish.
One must be careful not to remove certain cells and regions as the processes depend on them. Adding a drop down box would be fine by inserting a row or finding an empty space to do so. The program is designed to adjust the item description row size to the content; however this can also be done manually after the sheet protection is removed.
