It would be very helpful to be able to make a PDF and set it to "spreads" as you can in InDesign. When designing large display graphics that are made up of individual slices being assembled after printing, it makes proofing more difficult when art boards stay separate pages in the resulting PDF.
I'm surprised more people have not requested this feature.
My example: a greetings card with bleed image on the front and also graphic elements that bleed on the inside spread. I want to send as a pdf to a commercial printer as printer's spreads not separate pages. So it has to be imported into InDesign in order to achieve this, which feels long winded... : (