Hello folks, can anybody share any ideas, scripts or other resources to develop something to output only the pdf files? I have seen many websites like PDF manual Search engine which is offering free ebooks. Even a single search for the keyword 'seo' had brought this much resutls (see here - seo pdf manual and ebook download) I would like to know whether they are using google to get this results. Or any own scripts? I 'd like to know more about this topic. Please share your ideas and views to find it. thanks.