If you open the PDF in a modern Word (2013/2016/ browser version) it can be converted to editable text and then saved to one of many formats, including RTF and old doc (not docx), compatible with old Word versions… I don't understand why you need to use such an outdated text editor (there’s LibreOffice and Gdocs if you can't afford Microsoft stuff…) but anyway, I would use a new version to convert PDF and save into old doc or rtf.
The good thing is if you don't convert the PDF to Doc, there is a simple workaround: “Use notepad, open the PDF, and save in DOCX.” You really can't save PDF files in DOCX format because Adobe Reader 9 does not support DOCX files. A workaround is to open the PDF in a modern word (not Word 2010 or something), open it in notepad, and save as an .ODT file. Now your PDF will be converted into DOCX format, and you can save and open as one of numerous formats or in Word document with all formatting. I know that there is no way to have all these formats within the same file (notepad can't be a “plain text” file), but it is a simple workaround if you need to open a document format other than DOCX You will need an HTML editor: you need to have a text editor that can.