I have a 12" square brochure that they also want to print at 6"

I thought it would be easy to find an option in general to change the output size to 50% but there is nothing. The only way I can think is a ps file then distil it, but I don't have distiller. I could also just send the 12" and tell them to output the film at 50%, but that would leave me a little nervous. Anyone know a solution, or is there a demo of distiller maybe...i'll check that now.
Still, thought Indesign would have some option, maybe one that I don't know about