Layers

i have a 5 layer artwork. lets say a work pad. i did it 1 up 8.5" x 11" but now im going to print it but i need it 2up but my sheet size is 12x18 & i want to make sure my artwork is centered on the page. problem is when i select my 2up forms & tell it to center is centers everyhthing to the pg & messes up my art. so i have to tell it to Group. but if i do that It migrates everything to the same layer. i still want everything to be on its proper layer when the objects are centered to the pg.