GTh:People asking us to send them something they can print at their local printers.
Are you talking about standard US paper sizes that copy shops like Kinkos would be able to print from PDF on networked copy machines? If so, the standard sizes that I am aware of are letter (8.5"x11"), tabloid/ledger (11"x17"/17"x11"), and legal (8.5"x14").
GTh:From the websites of US printing companies I see paper size for 8 panel brochures of 8 inches x 17 inches or 8.5 x 14.6 inches, which doesn't compute.
8x17 and 8.5x14.6 could only be done on 11x17, and you could only get full-bleed on the 8.5x14.6, if that's a concern. 8x17 would give you 4.25" pannels, but 8.5x14.6 would only give you 3.65" pannels (slightly wider than a standard business card). You could print your 9.4" high pannels on 11x17, but you would be quite a bit short of the 26.8" width of your original.
To print what you have on 11x17 you would have to print at around 63.4% (if there is no bleed), but that may give the folder a little trouble getting the pannels to line up correctly.
What you may want to do is start with the printing process and work backwards. If you want everyone to be able to go around the corner to print this at their local shop, go with a maximum of 11x17 and retool the document to fit.