Acrobat Reader for Mac does not expose an Accessibility Tree to VoiceOver
Acrobat for Windows reads tagged PDF (aka PDF/UA) files and exposes an accessibility tree to assistive tech such as NVDA, Narrator, JAWS etc.
Acrobat for Mac does not do this. (And neither does Preview, or Safari). This means that the 'portable' document format is not accessible to Mac screen reader users at all. You can get the text nodes, but none of the semantic tags are respected.
Why is there such a discrepancy between accessibility support on the Mac vs. Windows versions of Acrobat Reader?
That's not what 'portable' means! Please address this as soon as possible.
Can you please provide the required information for us to fix the issue for you.
You will find the standard voiceover shortcuts here: https://dequeuniversity.com/screenreaders/voiceover-keyboard-shortcuts#vo-mac-navigation
Try this PDF, a flyer about the PDF/UA standard itself.
I am running Mac OS 10.14.6 and Acrobat Reader DC continuous release, version 2020.006.20042
Keyboard shortcut VO+Command+H should go from heading to heading. It doesn't.
Keyboard shortcut VO+Command+X should go from list to list. It doesn't.
(Compare with NVDA and Acrobat Reader for Windows).
Sure, you could try any of the PDF/UA files from pdfa.org, such as this one (tested with PAC3 and passes all PDF/UA requirements, tested also with Acrobat Pro DC for Windows Accessibility Full Check, passing all but manual checks). VoiceOver reads the text, but does not seem to 'see' or announce any of the tags.
Mac System is 10.15.1
Mac Acrobat Reader DC Continuous Release Version 2019.021.20061