Generally, windpuffs are a sign of over-riding an unfit horse. A horse who is not used to hard work who is worked hard over the period of a few days to a few weeks may develop windpuffs as the tendon sheaths of the leg become inflamed.
Now, if these are accompanied with adema, heat or pulses I would be worried however usually once they are there you're stuck with them. Cortisone injections can reduce the appearance although they can also introduce complications. It is safer to just leave them.
Make sure your horse is conditioned properly and that you are properly cooling out the legs after every ride, good luck!
They say money doesn't buy happiness -- well happiness doesn't buy horses!