I am trying to figure this out too. I am also wanting to print 2 per page with crop marks and have a middle crop mark.
Here's my process as reference for help. I set up my document size to the paper size I want them after cutting. I have the page amount divisible by 4, select booklet style, and add crop marks before printing to pdf. I know booklet style gives the assumption that I am folding the middle, but I get the same crop marks (edges only) when I simply export spread as pdf. I am hoping for a solution that doesn't involve making manual crop marks on a larger page. I would also prefer to keep them bumped up together in the center of the page versus having 2 separate pages with outer crop marks on a large page if possible. That is because one of the sizes I need would be A5 and I would like to have 2 A5 pages on an A4 page with a center crop mark only, but when I'm doing smaller pages I need both center and the outer edges. On InDesign when exporting spreads with crop marks it will automatically add a center crop mark.
Thanks in advance for any advice!