Do you have an Acrobat Distiller and/or other *.pc3 file already setup for plotting to PDF within AutoCad?
If so, you should be able to save a page setup that plots correctly (portrait/landscape/sheet size/etc.) using that particular *.pc3. Once in sheet set manager, you will be able to import that page setup to use for all applicable drawings/layouts. We do use sheet set manager although i myself have not plotted to PDF through it.