On Windows, Adobe Reader can export and view a list of comments through the Comment tab on the right side.
On Linux, Evince panel on the left has a drop-down annotations menu that lists comments. Press F9 if you don’t see the left-hand panel.
Not working for me
I have also read that you can extract all comments and annotations from a PDF file by
apt install texlive-latex-extra pdfannotextractor --install pdfannotextractor in.pdf
This yields a
.pax file without plain text, that it was not clear how to read.