I am running Adobe Acrobat Pro DC version 2019.021.20061 on a MacBook Pro with Catalina version 10.15.04. In the Adobe Acrobat preferences I have autosave set to every 5 minutes. However, when Adobe Acrobat decided to restart for me to agree to some updated user terms all my comments on the document disappeared. From a quick google search it is clear that this is a common problem and that the autosave feature is not working, or at least only occasionally.