Imposition software is available that automates the process, usually during the printing stage. You send the document to the printer as normal, but the imposition software replans the order of printing so that the sheets come out as per the required layout. What happens, however, if there is a paper jam? Such additional software utilities may suit some people, but I tend to find them all one big hassle. I prefer to see my pages in the word processing program as they will be sent to the printer. If a paper jam occurs, I can easily print off a duplicate later on without disturbing the current sequence of pages. My method, however, does result in a lot of A5 offcuts, but I don’t waste them. I use them for making notepads or just giving a few hundred sheets to the neighbours if they have children in the family who like drawing or painting. I arrange my pages in the word processor by having the left-hand (even) pages close to the right edge (landscape format) and the right-hand (odd) pages close to the left edge.
When I trim the sheets to A5 I then only have a single cut to make. And three sides of the sheet, including the all-important spine, remain nice and square with their factory- guillotined edges. Squaring up the spine is very easy this way.