The official answer is here. But it requires some trial and error. I found a very simple way. Rather than asking the user (or customer) to find out this information, it is simpler to detect it myself. I ask the customer to send the screenshot of File menu to me. That shows the version number easily.
2003 and before – File menu has a Page Setup menu option.
2007 – NO File menu. Instead there is a round, colorful button
2010 – File menu has Save and Send option
2013 – File menu has Share option
Simple and effective. Works all the time.