If you’re confuse to find articles, journals or e-book in FDF file, I’ll let you know that there are a lot of specialized search engines that let you find and download PDF files. You could find any PDF by simply adjusting a few search settings and boolean terms. You don't need to do all that anymore. PDF search engines are emerging to eliminate that task.
So, you do not need to be confused anymore because pdf search Engine is a search engine with a simple appearance, much like Google. You simply enter the keywords that show you are looking for PDF files. Then PDF Search Engine will look for you. Since all results are linked directly to the PDF file, you can easily download PDF or view them from your browser on the fly. However, they can be hard to use if all you see are lists to linked PDF without any visual recognition to check if you are downloading the correct file that you need.
Before downloading, you can catch a glimpse of the contents of a PDF that you find. So you do not need to waste time to download a file that apparently useless contents.