Would leather pants be acceptable as semi formal attire for a women?

Absolutely, this fall leather pants will be back! Although, be carefull not to overdo.... so no leather jacket with a pair of leather pants unless you are a biker.

On the other hand, if you're going to wear leather pants, wear some type of leather shoes, preferably boots of a similar color (black with black, brown with brown, etc.) Leather pants with sneakers just looks bad.