“I know a tool which has this function.” That is VeryDOC PDF to Word Converter and you can get it from here.https://www.verydoc.com/pdf-to-word.html
After downing and entering the interface of this software, you will see on the menu list that there is such a function button.
What you need to do is just click this command then you will get the MS Word DOC format form PDF file. Then open DOC file in MS Word 2007 or Word 2010, then you can save to DOCX format.