I would like to be able to print a different invoice template for a selected processed order - for example, a P91 form in an invoice template, or a prepaid returns label, also designed on an invoice template.

It would be very useful to be able to reprint specific template invoice for processed orders. At present it's a bit of a nightmare when you need to reprint a copy of the invoice for some reason.

Yes, once you've clicked processed, you've had it!

When in processed orders right click, print invoice will print the default invoice for that order. The trick is to set a condition on the invoice template you want to be printed (in Settings->template designer->edit->printing conditions). I usually set a condition like nOrderId=123456 (where 123456 is the processed order you want to print the invoice for). Then return to open orders, right click the required order, print invoice et volia!

seems such a basic need for all users, I get customers asking for copies of invoices all the time (after processing), i have set up the default so it doesn't show payment info (as i sell gifts) all it needs is a right click print specific invoice (as happens in open orders!)

Fantastic news, looking forward to this!