Like most other people, I have been using Adobe Reader as my prefered pdf reader for a long, long time. Some time back, I installed Foxit Reader to try it out, but it never, really caught on.
Recently, however, I discovered that the default setting for pdflatex (or maybe it’s just the default for the pdf format?) were to disallow comments, as can be seen on the screenshot below.
In the end, I opened the document in Foxit reader, and it had no problem adding comments. It did, however, have the annoying “feature” that it used the username of the logged on user as the name for the commenter. And I were unable to set a global name for it to use, so I had to edit every, single comment.
And it didn’t look as well as it should in Adobe Reader. Go figure.