Word processors software like Microsoft-Word are terrible programs, because they do not standard check or clear styling of a document. They have to choose the simple way, because users are a PITA and very unpredictable in their use of the program!
Users generally make a mess of their document, where styling is concerned, they cut and paste and move texts, without realising what this does to the styling, that the program tries to keep.
To bypass it, Microsoft invented the %$&#&# .docx extention, but that is only a type of zipped .doc file!
To test your document save it as html and open it with a plain text editor program like Notepad++ to see, what a mess it contains, like double styling for each and every paragraph. That why, knowing the difference between an enter and a "shift +enter" already makes a big difference. (Enter = "end of paragrapg", Shift+enter = "new line")
It seems that under Word, CTRL+SHIFT+R deletes duplicate styling, so open your largest document, hit CTRL+A, to select all text and then hit CTRL+SHIFT+R and save it under a new name and compare its size!
If everybody would do this, esspecially for all Company and Govermental documents, we could save a whole datacentre of data storage!