The comments all were added inside Acrobat using the native tools, and thus they ARE Acrobat comments, i.e. not imported from the original file.

The Comment tab shows all of the comments, and the document prints with the displayed comments wsiwyg to the screen display.

I must be missing some little twist here: I followed the help instructions literally when going into Document, Summarize Comments..., but clicking OK on this dialog simply dismisses the dialog and produces no commented pdf version. LIkewise with Print Comments...