Judging from the answer to this question, one cannot change the page size etc from ArcPy, so I set up my "template" mxds so my script can save a new copy of it, change data sources etc. This methods works perfectly for my A4 maps.
However, my A0 mxds are losing the printer and page settings from the template. My
A0_template.mxd is set to print from the plotter on A0 paper using the default printer settings. After the copy of the mxd is produced and I open it, the printer has somehow changed to the normal small printer with the paper size matching the default tray. I am simply using the
saveACopy(filename) method which is part of the MapDocument class. Why would the correct settings for the A4 mxd be saved, but not for the A0?