PDF Extension is the thing that helps you to identify particular file operating system and from which it got in exist. One can easily get complete identification of the file and it help user to know about the file generated origin. For example, if the file has .doc extension it means the file is created through the Microsoft Word. And it can be only opened through MS Word only. There are so many types of file extensions exist. They all have their own behaviour and activity to work with platform. PDF File extension often followed by three or four characters. File extension provides the complete details about the certain file which helps us to open that file with suitable software as well. This means one cannot open the file of different File extension with another software system. It is almost impossible to do so. This is why every publishing software like MS Word, Notepad and other media files software has their own file extension. This enables them to do such activities with same atmosphere which they got in the initial stage.