It would help if you showed us the code - in particular, the calling sequence, and values of parameters passed.

The area that is failing is:

sub content {
    my ($self,$obj,$dir) = @_;
    if(defined($dir) && $dir>0) {
        $self->precontent($obj);
    } else {
        $self->addcontent($obj);
    }
    $self->{' apipdf'}->new_obj($obj) unless($obj->is_obj($self->{' ap
+ipdf'}));
[download]

and it appears that "$self->{' apipdf'}" is not defined.
Has that been setup properly , perhaps by calling the "coerce" method ?