View (manu) > Hidden geometry. When you create a circle and immediately afterwards type a number followed by a letter s (like 48s) and hit enter, it will have that poly count. Also, until you do something to the circle (say extrude it), you can right click on the edge and choose "entity info" where you can still change the segment count (both methods work for the polygons, too). The free version is only limited in its export functions mainly and all modelling tools are equally available with the pro version.