use PDF::API2;
my $big_pdf = 'big.pdf';
foreach my $souce_pdf (@pdf_files){
        my $pds;
        eval { $pds = PDF::API2->open( $source_pdf ) };
        if ($@) {      next;    }
        my $pn = $pds->pages;
        $big_pdf->importpage($pds,$_) for 1..$pn;
    }
$big_pdf->saveas;
$big_pdf->end;