use CAM::PDF;

my $doc1 = CAM::PDF->new('label1.pdf') || die "$CAM::PDF::errstr\n";

my $doc2 = CAM::PDF->new('label3.pdf') || die "$CAM::PDF::errstr\n";

$doc1->appendPDF($doc2);
$doc1->clearAnnotations();

$doc1->cleanoutput('campdf_result.pdf');