Batch conversion of files in Windows Command Line (cmd Win x64 or Powershell) using a .bat Script file. Here it's a batch conversion of various document type files to Adobe's pdf format. But essentially the process is the same for any batch conversion with the for construct in cmd.
For using this script for pdf batch conversion install the latest version of calibre from : https://calibre-ebook.com/download_windows which will give us the command line module ebook-convert that can be used for conversion.
Simple double-click on the convert_to_pdf.bat after placing it in the appropriate directory or invoke the script from the command line for converting .mobi,.epub,.djvu,.chm,.lit,.azw3 files in the directory to .pdf.
Also convert.bat can be used for operations and conversion of other file types in a similar manner.