If you are interested in this topic and you want to get translated article please let me know in Discuss comments bellow.
With Copy&Paste from Word document you will usually get ugly code with unwanted tags as span. You can paste without formatting using CTRL+SHIFT+V shortcut but you can’t ask editors to remember and use it. Fortunately CKEditor itself allows you to configure it this way, now I will show you how to do it in Drupal.