Did you buy Pro for $18.88 USD from www.limewire.com ? After purchase, you should've recieved an email with a link to your Pro personal download page (you don't have to give your email address to download from that page). If you don't remember recieving that email, just check that it hasn't been marked as spam by mistake.

If you did buy from the official site, see the thread below. There are lots of links for different issues. If you're stuck, send a PM to limenathan
Problems getting your LimeWire Pro after payment or other Pro payment issues etc