Printing on even pages

I have a report which prints out Invoices. These invoices include term's and conditions as the last page. I have an external program which emails out the batch of invoices to the accounts department. If they print off the invoices double sided, i could have the problem in where an invoice is three pages including the T&C's and then there could be another invoice after that. If there is, the T&C's would be on the page and if you flip it over, you will have the start of a new invoice. I hope i've made myself clear here. lol. So my question is, how can i make it so that the T&C's print out on an even page?