How to change a 1:100 scale into a 1:200 scale?

If I have a printed drawing in 1:100 scale on a1 paper can I photocopy it and change it into a 1:200 scale or do I need to make it 1:200 before hand on CAD and then print? Wil it automatically change into 1:200 when I photocopy to a3 paper?