This is brilliant:- http://www.martin-schenk.es/en/cakephp-2-pdf-with-tcpdf/

in View/Layout/pdf/pdf.ctp

<?php
 
header("Content-type: application/pdf");
 
echo $content_for_layout;

But with google chrome using the $pdf->Output('filename.pdf', 'I') option you get the raw text of the PDF to the screen in other words garbage.

However if you remove the header from the layout:

<?php 
echo $content_for_layout; 

And then add the following to your controller

 function create_pdf($id = null) {
        // logic and options here

        // this is what you need to render
        // tcpdf output to an I (inline) target for 
        // Google Chrome
        $this->response->type('application/pdf');
        // ...

    }

Following the recommendation from http://stackoverflow.com/questions/16048922/cakephp-2-x-tcpdf-output-chrome