Yes. I did this a fair bit back in the 90s and then again for a while in a particular context around a decade ago.
Newton Connection Utilities and NewtonWorks allow export as plain text, ClarisWorks format (CW v.4 would be about the right vintage), and either .RTF or .DOC for Word, I forget. And there is a similar import function, of course.
In my experience, transfer of content from the MessagePad to the Mac worked best if the target was Word, right up to Word 2001 in OS9. Such transfer of content was even capable of preserving graphics in the NewtonWorks file. ClarisWorks was not so good at graphics, which is a bit counterintuitive, but there you have it.
I did not do much importing from Mac to Newton, but going the other way from Word would have to be less reliable -- e.g., in relation to footnotes and named styles. The Newton did not do footnotes, NCU could not deal with them, and NewtonWorks itself did not have named styles of the Word variety, but just local styles. Word itself, of course, is built around named styles, so you would be bound to have frustrations, even if content were kept simple, owing to the way Word works, if going back and forth between the two platforms. As we all know, Word is fussy, so at this point, ClarisWorks might have advantages, but I can't say for sure.
There were add-ons that gave footnotes and named styles in NewtonWorks, but they were third party, licenses today are usually unobtainable, and it is hard to imagine that those modifications to Newton software meshed with NCU anyway.