This will be very short. One word: Word. Use MicroSoft Word 2016 to open your PDF file and save as a word docx file.
Don’t be scammed to download all those junk and fake-open-source software like “UniPDF or Nemo or Free PDF-to-Word Converter” from Internet. Don’t install any software from any unknown websites, especially those with all sorts of ads posting everywhere. 99% of their software are virus.