pdf-annot-text.pl

#!/usr/bin/env perl
use strict;
use warnings;
use feature qw(say);
use Encode;
use PDF::API2;

my $pdf = PDF::API2->open($ARGV[0]) or die;

for my $p (1 .. $pdf->pages) {
    my $page = $pdf->openpage($p);
    next unless $page->{Annots};
    for my $a ($page->{Annots}->elementsof) {
        $a->realise;
        next unless $a->{Contents};
        my $text = $a->{Contents}->val;
        eval { $text = decode('utf-16', $text); }; # error in ascii string
        $text =~ tr/\r/\n/;
        say encode('utf-8', $text) if $text;
    }
}