Hey Tom,
My design was also used for a booth, and it finally worked out ☺
In utter frustration I sent the design both scaled down and split into 2 artboards/PDF pages for the print shop to scale up in the final print and combine. I don’t know how they put them together but the banner was printed in one piece, 2.5×8 metres. I had my doubts about how far I can scale up vector graphics in PDFs but several people, including yourself, confirmed that it’s not an issue, and I saw it myself in the final print.
My bigger concern of course was with the raster images! Before splitting it into 2 artboards, I tried scaling down the entire design on a single artboard to the max possible PDF size to protect the images. It wasn’t a very good idea ???? The PDF was too large and a wide strip of the banner (about half a metre) wouldn’t render anything except for the logo. Hence I split it into 2.
Anyways, I got a good answer from the Adobe forum regarding the matter:
A PDF can always be resized, so 1. is the obvious choice.
Just make sure that the AI document/file is made with the right/sufficient resolution for possible raster effects and raster images.
The size (in pixels x pixels) in raster images should correspond to the desired resolution at the full/final size (2.5×8 m), and the resolution of raster effects (Effect>Raster Effects Settings) should be twice the desired value at the full/final size (2.5×8 m).
Obviously, the desired/needed resolution depends on the intended viewing distance, you may ask the printing shop.
Here’s the link to the full discussion: https://forums.adobe.com/message/10179570#10179570
Good luck on your September design 🙂