How to Create Press Quality (Print-Ready) PDF (PDF/X-4a) with Acrobat Pro from Word for Mac (.docx)

I downloaded Adobe Acrobat Pro DC yesterday: Version 2002.001.20112.

My computer is running Big Sur: Version 11.4.

I have a document in Microsoft Word for Mac: Version 16.60.

I want a Press Quality PDF (e.g., PDF/X-4a) for print publication.

I can get a Web Quality pdf (File > Print > Save As PDF) or a Best for Printing pdf (File > Save As > File Format > Export Formats > PDF > Best for printing), but the quality isn't high enough.

I have seen how a Press Quality pdf is created on a PC: Export > Create PDF/XPS Document > Options > PDF Options > ISO 19005-1 Compliant (PDF/A). But these options aren't visible on my Mac.

Acrobat Pro > File > Create > PDF from File seems to force create Web Quality with no Options menu for Press Quality.

Acrobat Pro > Tools > Create PDF has Advanced Settings but it’s greyed out.

How do you create a Press Quality PDF (PDF/X-4a) from Word for Mac?

Any help would be appreciated.

P.S. The Adobe Word to PDF online converter seems to only offer Web Quality. Is there another URL for Press Quality?