Programs enabling conversion of the file:
If your objective is to convert the file from EPUB to the file KF8, you can use any of the applications listed. EPUB to KF8 conversion process in every program intended for this purpose (so-called converters) is very intuitive and everyone is able to manage converting a file.
However, bear in mind that the list may also include programs to support and work with the indicated extensions EPUB and KF8 - and not only converters. In such a case, you need to open the source file EPUB and from the options available in the program, choose ”Save as... KF8" or "Export to KF8".