You are getting the error "Can't call method "getRootDict" on an undefined value" because 'new.pdf' doesn't exist.

Manipulating PDF files is quite complex and I found that I had to use both modules to achieve what you are trying to do as PDF::API2 doesn't seem to have any way of extracting text and CAM::PDF doesn't seem to have any way of adding an empty page.

Hopefully this will help you on your way:

use strict;
use warnings;

use CAM::PDF; 
use PDF::API2;

my $pdfone = CAM::PDF->new('input.pdf');
my $pdftwo = PDF::API2->open('output.pdf');

my $font = $pdftwo->corefont('Helvetica-Bold');

for my $pagenum (1 .. $pdfone->numPages() ) {
    my $text = $pdfone->getPageText($pagenum) or next;
    my $page = $pdftwo->page(); # add a new page
    my $pdf_text = $page->text();
    $pdf_text->font($font,12);
    my @lines = split("\n",$text);
    my ($x,$y) = (50,700);
    for my $line (@lines) {
        $pdf_text->translate($x,$y);
        $pdf_text->text($line);
        $y = $y - 20;
    }
}
$pdftwo->saveas('output.pdf');
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