use PDF::API2;

my $result_pdf = PDF::API2->new();
my $pdf = PDF::API2->open('label1.pdf');

my $page = $result_pdf->importpage($pdf, 1);
$pdf = PDF::API2->open('label3.pdf');
$page = $result_pdf->importpage($pdf, 1);

$result_pdf->saveas("pdfapi2_result.pdf");