For Readiris 14, 15, 16 and 17, if you purchased a standalone version, the 34 characters activation code should be located in the confirmation email sent to you after your online purchase.
If you received Readiris with an IRIS scanner (IRIScan Book, IRIScan Anywhere, IRIScan Pro) or a HP one, you have to connect your scanner with a USB cable before starting the software. The activation code will be generated automatically. Click on "Activate" and the software will be activated.
Mathieu Quintin