Try something like...

my $printer  = Wx::Printer->new;
my $print_data = Wx::PrintData->new;
my $page_setup_dialog_data = Wx::PageSetupDialogData->new;
$print_data->SetOrientation(wxLANDSCAPE);
$page_setup_dialog_data->SetPrintData;
[download]

Untested. From reading http://docs.wxwidgets.org/trunk/overview_printing.html

James