AFAIK: this is not really an option within Access.
There are some real kludge workarounds using the sendkeys method; however, they are dodgy at best. Your best bet is to see if this is an option with your printer. Mine at home doesn't have this option; however, several of the printers at work have this option; however, I've never had the need to do this type of printing :-)
Two thoughts, neither of them have I tried myself, if the printer properties isn't an option for you:
a reverse sort order on the underlying record set. This may not be what you desire if the report and page headers are setup.
Another option would be a loop using the
DoCmd.PrintOut Method (reference). Open the report in preview (or hidden) assign the report as an object and then use the page count property to return the number of pages in the report. Once again, I don't know how this will work with page and report headers. I would hope that once opened the report would be properly formatted; however, that may not be the case with very complex reports or reports that have VBA behind them.
Just out of curiosity, why do you need the pages in reverse order?