Re order a PDF and zip to PDFs

How do I reverse the page order of a PDF and then how can I “zip” to files together so it takes 1 page from each PDF at a time.

The reason for this is a have some large documents that are double sided and when I scan them I end up with two PDFs docs the first is all the odd numbered pages and the second is all the even numbered pages but in reverse order.

Any solutions?