1. Use revtex and set the format to preprint.
2. Open a command window in Windows and run the following command:
htlatex yourfile.tex HTML
3. Open the generated html file in Microsoft Word and change the fontsize to 12 and line spacing to 1.5 lines.
4. The reference links in the manuscript do not work properly. To remove these hyperlinks, select all ("CTRL+A") and press CTRL+SHIFT+F9.
5. There is no line break in the bibliography. For a better format, use PDFLatex to generate a PDF manuscript instead, convert it to Word using Adobe's free online tool (or that comes with Adobe Acrobat), adjust the page margins to be the same as the html file in Word, and copy the bibliography to the html file.
6. The equations are converted to pictures. Double click them to adjust their sizes if needed.
7. These pictures are linked to the png files generated by htlatex. They will not display in a different folder or on a different computer. To convert them to embedded pictures, go to File->Info->Show All Properties, and click "edit the links to this file." Then check the box at the bottom that says "save pictures" or something similar and click the button on the right to remove links.
Now, you may ask me why not directly edit the Word file generated by Adobe Acrobat. The issue is that many subscripts of inline maths are converted to pictures or letters in a separate line, which are very difficult to edit one by one. The same issue exists for a few other online converters I found.
If you know a better way to complete this task, please do not hesitate to let me know!
(Updated on Jan 2, 2024: I just discovered that arxiv now provides an HTML version of the submitted manuscript. The downloaded HTML file is very complicated though and does not display properly in Word. Also, pay attention to the order of the references in a single citation. They are ordered and grouped automatically by latex in PDF/DVI output but not in HTML, as each reference has its own hyperlink.)
