If you have the correct printer driver (or .ppd file) for the printer/plotter in question you should be able to choose it and set the correct page size.
If the driver isn't available, you could in page setup select a page size half as big as your goal and set page scaling to 50%, produce your pdfs and then instruct the printer to scale them up when printing.
The publisher works just like ordinary printing. The important consideration is to set the master layout at a size that works to print at the available paper size, either at 100 % or scaled.
AC4.1-AC26SWE; MacOS13.5.1; MP5,1+MBP16,1