This addon works well enough if you are very undemanding. You can't customize the document, before it is created. The built-in PDF printer in Linux is more versatile in this regard. And this addon exhibits the typical Web -> PDF conversion errors: content consumes the whole paper page, i.e. no margin and page breaks cause funny text breaks. Just another example of how insufficient the paper model is in the digital age. My suggestion: ditch it and just save the web page (Ctrl+S).

Edit: Web page content is sent to pdfmage.org. They promise to delete documents after 10 minutes. A privacy policy is missing.