PDF: how to stack for printing?

[FlipSide]

Hi,

I'm trying to set up a document for printing.

what i have:
a 3 panel a4 brochure created in indesign.

what i need to do:
i have to send the final file as a PDF to printers. how can i create a file so that the "outside" is stacked vertically (a3) so that there are 2 a4 files?

i need to do the same with the inside. so in the end i'll have two seperate PDF files for printers (1 x outside, and 1 x inside)

so "outside_1" = 2 x landscape a4 (stacked vertically)
so "inside_1" = 2 x landscape a4 (stacked vertically)

can anyone tell me the fastest way of doing this....i've spent hours trying to get the correct result.

thanks in advance!

PS: I need the cutmarks and bleed set up in that of course. thanks