#!/usr/bin/env perl

use strict;
use warnings;

use PDF::API2;

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

for my $page_num (2 .. $src->page_count() - 1) {
    $pdf->import_page($src, $page_num, $page_num - 1);
}

$pdf->save('DXout2.pdf');

##</code><code>##

$ ls -al
...
-rw-r--r-- 1 ken None  3855 Mar 25 09:10 DX.pdf
-rw-r--r-- 1 ken None  3277 Mar 25 09:42 DXout.pdf
-rw-r--r-- 1 ken None  5525 Mar 25 10:46 DXout2.pdf
...