Do you want to display the PDF in the browser window? If so, you have to use Suitelet, not restlet.

That’s what we learned that we have to send the content, and have it generate PDF in Salesforce.

In that case, the restlet has to send the base64 content of the file back to SFDC. So, once you render the pdf, get it's value and use response.write to send it back.