You can use plot configuration manager "PlotConfigManager" to get the current plotter device used by AutoCAD. Below code shows the procedure.
[CommandMethod("CurrentPlotDevice")]
static public void CurrentPlotDevice()
{
Document doc = Application.DocumentManager.MdiActiveDocument;
Editor ed = doc.Editor;
try
{
PlotConfig config = PlotConfigManager.CurrentConfig;
ed.WriteMessage("Current plot device :"
+ config.DeviceName);
}
catch
{
ed.WriteMessage("Unable to get the" +
"current plot comfigartion\n");
}
}