I like the feature where existing marks on the pdf can be erased so new text can be added. This was especially helpful when correcting rebar schedules when there was no room above or beside the original text to enter a change. This may have been available on version 9 but if so I didn't find it. I was using a trial version at the time so I didn't have a lot of time to try everything before my trial ran out.
One thing I haven't figured out yet is how to revise text I have put on the drawing after I have left that portion of the text. I have been erasing and starting over again. I will continue to investigate.
It would be nice if some of their tools functioned more like autocad functions but I realize their may be copyright issues if the were too close.