How to differentiate between articles, conference proceedings, etc.? I have many PDF files for some academic papers. I want to sort them into journal articles, conference proceedings, reports, etc. 

How can I know which one is an article and which one is a conference proceedings and which one is ... (any other type of papers)?
Reference managing software such as Mendeley usually provide an import feature for PDF files. You simply supply a list of PDF files and the software automatically extracts the metadata such as title, author names, journal, and so on. The accuracy is usually pretty good, and then you can easily sort and organize the files in whichever way you want.