PDF (Portable Document Format) is a versatile electronic document format. It was initiated by Adobe and was originally intended for electronic presentation of printed materials. Hence, the tasks of this format follow - storing information about the color scheme and the arrangement of elements, as well as ensuring identical output on different monitors and printers. PDF documents can be opened using the free version of Adobe Reader or a web plug-in that is available for most Internet browsers. In some browsers, in particular, in Google Chrome, this format is supported even without the plugin installed. You can edit PDF files using the paid version of Adobe Reader. Also, there are a huge number of programs for both opening and working with this format, and for converting to other formats.
Fans of electronic books at least once came across the FB2 format and did not understand how to open it on a computer. There are many free programs available for reading FB2, which are also great for text files of books of all formats. FictionBook is an electronic book format formed as an XML document, where each element is described by tags. The FB2 format is designed to be compatible with various devices and other formats. Documents are quickly generated using XML. They are already ready for use, revision and editing - all this is done through programs. Documents with the FB2 extension contain, in addition to tagged text, images, attachments, and structural markup. There are no problems with opening the format on e-books - the corresponding software is installed in them initially. But when reading from a tablet or PC on Windows OS, you will have to tinker.