It's very rare that a snow leopard will attack humans unless the human is a threat to the snow leopard.
It has not been reported that snow leopards attack humans but it is possible if the snow leopard sees the human as a threat or the human is trying to hurt the snow leopard or any of it's babies then it may decide to attack you.
Usually though the snow leopard will avoid the fight and take off the other way if possible.
Snow Leopards are pretty gentle animals and will usually be very friendly around humans but you should still use caution when around them because anything can happen.
The sow leopard is considered to be one of the less aggressive animals when it comes to big cats being aggressive.