Hi guys, I'm new to apple product. And now, I just notice one problem with my macbook pro. Every time I open a pdf file that contains the integral symbol, it's just black out. And sometimes it also happens to - or + symbol. When I saw the same file on windows, it just appear as it should be. Can't mac detect the symbol that's created in windows? to explain about my problem, I've attached a picture of what I'm seeing (and what is being printed off) from my Mac. the circle is the "disappearing" minus sign and the black line is the integral sign. Hope that someone can explain or give me an advice on how to solve this problem (maybe I need somekind like application or so..) thanks !