PDF format is used when you need to save files that cannot be modified but still need to be easily shared and printed. In rich textual and graphical format. So converting PDF to any other format is generally not required. For converting any document to PDF can be achieved by individual software itself. e.g. MS office can export document to PDF. OR you can print any document as pdf file. OR there are online services which help converting almost any document to pdf.
It took me a while to figure out how to convert PDF. Here is a link to one of my answers Also, I am not going to recommend it to everyone, it is a paid version. So make sure that you are a member, or you will not be able to download it for free. There is a free version available.