If your Pro is less than 6 months old, just go to your personal download page (that you got a link to when you bought Pro) & download the latest version.

If you haven't saved the link, go here & enter the email address you used to buy Pro
http://sales.limewire.com/support/pro_lookup.php

If your pro is more than 6 months old, your email address won't be on the database... you'll have to buy again.