Expanding Word track changes comments in Adobe pdf

Hi, 

I have converted a Word document with changes tracked into a pdf. I am viewing the pdf in Adobe Acrobat. It all shows up ok, except that I can't see how to expand the comments that are too long to fit on the page. The long comments show a '...' in the corner, but when I click on it nothing happens. I feel I must be missing something simple to expand the comments. Any help much appreciated, thanks!