Hi,
Simply set your camera size to 0.5 ( it should be 1 currently), and everything will be twice as big.
But yif you are looking to keep everything int he same screen position, then you will likely have to move your stuff on screen.
also, there is a scale factor on your objects ( the transform itself, or actually the sprite definition itself). I know you don't want to edit your objects, but I am not how it's feasible without editing them otherwise. Maybe someone will step up with the right solution.
bye,
Jean