Unfold each paper in your design, create guides for the folding lines, look how the printer wants the PDF and export it that way.
Is this something you are printing or is it going to a commercial press?
I was planning on printing it myself. I have an Epson 1430, but it's giving me some issues with printing on vellum. So I might take the final draft to commercial press. For now, I'd say i am self-printing.
It's really an imposition problem. If you are having it commercially printed the printer should be able to do the imposition from a regular facing page document. If you are printing in house you'll have to set up printer spreads (Print Booklet won't work for french binding).
In your example photo pages 2-3, 6-7, 10-11, etc. are on the hidden inside pages and pages 1, 4-5, 8-9 etc. are the visible text pages. So here I have reader pages on the left and imposed printer spreads on the right. Printing from the imposed document, spread 2 would back up to spread 1, spread 4 backs up to spread 3 etc. You would fold on the center line and the binding is on the outside.
You can create an imposition by placing the pages in a new document, which is what I've done here, or you can work in one doc setup as printer spreads. My facing page reader document is 4x5 and my imposition is document is 8x5 single pages.