hi ! i am beginner in auto cad 2007. working in real estate field. i have two separate file in auto cad , i wanted to check how to super impose one dwg on other.

Best option would be to xref one drawing into another.Another option would be to insert, as a block, one drawing into the other.

sir, thank you for prompt reply, i copied dwg. and pest on other but it shows difference in size. how to over come this 

You would have to scale the drawing either up or down to make it fit.