When you use the demo version of VMInvoice, you have mainly 2 limitations:

1) The software will only work (import orders, customers and products) from our Virtuemart test e-commerce (http://www.vminvoice.com/vmsite).

2) You can't save more than 20 invoices and you cannot print on printer or export and on prewiev you'll have a red band.

To use VMInvoice without these limitations, please purchase the complete version.