use 'sheetset', create a new sheet set with existing drawings, select the ones you want and then you have .dst file. If all your page setups are set correctly, then you can plot all of these to the plotter named in page setups, or better still create a dwt. file with page setups for all sizes, including A3 fit, PDF's, DWF's etc.
e.g I can plot all of my Mech drawings with a few clicks (without opening any of them) to correct size, PDFs etc - a very useful tool.