Comments in PDF seem to be something that's only available using the official Adobe toolchain, e.g. this comment in the discussions to a recent (end of 2006) survey of PDF applications on GNU/Linux seems to sum up the situation:
http://applications.linux.com/comments.pl?sid=37658&op=&threshold=0&commentsort=0&mode=thread&tid=47&pid=93375#93389 It should be that with the fight over standard specifications for government documents heating up across the world Adobe will help make comments createable on GNU/Linux http://redmonk.com/sogrady/2007/01/30/iso_pdf/ For now, it seems that practically it's a very restricted format for sharing documents. Oisín
