suggested removing Compress::Zlib

That's a bit strange (because Text::PDF::FlateDecode depends on Compress::Zlib).  But if it works... ;) — although a better option might be to properly install Compress::Zlib, such that it works (it in turn depends on the C library libz (aka "zlib")).

# from Text/PDF/Filter.pm

package Text::PDF::FlateDecode;

use strict;
use vars qw(@ISA $havezlib);
@ISA = qw(Text::PDF::Filter);
BEGIN
{
    eval {require "Compress/Zlib.pm";};
    $havezlib = !$@;
}

sub new
{
    return undef unless $havezlib;
    my ($class) = @_;
    my ($self) = {};

    $self->{'outfilt'} = Compress::Zlib::deflateInit();
    $self->{'infilt'} = Compress::Zlib::inflateInit();
    bless $self, $class;
}
[download]

And CAM::PDF goes like this:

sub encodeOne  ## no critic(Subroutines::ProhibitExcessComplexity)
{
   my $self = shift;
   my $objnode = shift;
   my $filtername = shift;

   (...)

      my $filt;
      eval {
         require Text::PDF::Filter;
         my $package = "Text::PDF::$filtername";
         $filt = $package->new;
         if (!$filt)
         {
            die;
         }
      };
      if ($EVAL_ERROR)
      {
         warn "Failed to open filter $filtername (Text::PDF::$filterna
+me)\n";
         return 0;
      }
   (...)
[download]

My guess would be that if that routine returns false, the PDF's content streams simply remain uncompressed  (which is valid PDF format, too, but larger...)