Currently when a report is generated, the default page order is across then down. 
If a report spans several pages (both horizontal and vertical) it may make more sense to order the pages such that they print down then across. Our reporting requirements would need to be able to set this option in the code as the report is being generated and before it is passed to the report viewer.

A working example of this feature can be found in the page settings interface for MS Excel. A snapshot has been attached.