The best pdf reader I have used so far. So many extra tools and options available than adobe reader. Some of the features include different types of underline, multiple documents can be opened in same window under different tabs, pen and eraser like paint, text note can be added at any point, it also allows document conversion to other formats.
Using this for a long time and I have rarely seen it crashed. The best feature is that it remembers the the page on which document was closed so that on opening it again it directly open the last seen page.