A quiock update, at least partially answering my own question ....

I have solved this problem, at least as far a Word is concerned (which is all that really matters to me).

Although it took a lot of time/effort, as is so often the case, once found the solution was very simple - and, fortunately, it was not due to any issues of obsolescence, 'unsupportedness' or incompatibilities of the applications/OS involved.

The problem was some rogue registry entries for Word file associations which were not apparent by using ASSOC / FTYPE. Once these were sorted out, the Word formats (.doc, .docx, .docm, .docb) immediately appeared in Acrobat's 'supported file types' list, and all functionality was as it should be.

I have found, and corrected, some similar registry issues with PowerPoint, but Acrobat still does not recognise any PowerPoint file types as 'supported'. This doesn't really matter to me, but I suspect that I need to take a finer toothcomb to the registry. It's certainly not 'far off' working, since a right-click on any PowerPoint file enables one to successfully convert it to PDF (using Acrobat's 'engine'). If I find the (probably, again, 'simple') solution to this, I'll report back!

Kind Regards, John