I would check out how I Save As and save the doc to the lowest version I think any user will use

As for Apple use, no idea

Unfortunately, changing Word docs between Macs and PCs is not seamless. For one thing, the fonts are not identical, so line breaks may differ from Mac to PC. Make sure you only use the standard fonts that are installed with Office. If you use other fonts, including symbols (such as bullets) they won't translate well.
Also check that the default page layout is the same on both machines (i.e. Letter or A4) and the page margins. Check this when you open the document on both machines.
Word is not ideal for page layout for these reasons. Maybe you could send a PDF for checking?
Ideally, use the same version of Word for the initial layout as you will use when you print the document.
Cheers