QPageSetupDialog( myPrinter) uses the default printer instead of myPrinter for the initial drop down menu selections.

when QPageSetupDialog is expressly provided a specific non-default myPrinter, then the setup dialog should use myPrinter and not the default printer for the initial settings.

QPrinter *myPrinter = new QPrinter(
            QPrinterInfo::printerInfo(QString("Brother_PT_9500PC"))
            );
QPageSetupDialog pageSetupDialog( myPrinter);
if( pageSetupDialog.exec() == QDialog::Accepted )
{
    // ...
}