Here is the latest release of the DeDrm plugin for the Calibre 5.x version, meaning with this version, you can convert your kindle books to pdf using the new Calibre. You will not require the older version Calibre 4.23. Simply download the new Calibre and use it with this DeDrm. All download links are provided below.

Please note THIS VERSION SHOULD BE USED with the CALIBRE 5.x. If you are using the older calibre 4.x you should be using the older DRM i.e. 6.8.1.