You are most certainly welcome to print a replacement ticket for yourself. Instructions for doing so can be found HERE. However, this ticket will be identical to the one you no longer have, barcode and all.
Tickets can only be scanned once for entry to the event. If the previously printed ticket winds up in the hands of anyone else, and they use it before you do, you will be denied entry to the event.
For this reason, we always recommend placing your tickets in a safe place after printing them out. Treat your tickets as you would cash and keep them safe!