Microsoft Powerpoint appears abnormally on my iPad

When I open a powerpoint file during a lecture in class, a lot of the formatting is whacky and some symbols end up being squares. Some words will overlap and formatting is just all messed up. Because of this reason, when I convert the powerpoint to a PDF file or open the file to Dropbox to save it, these formatting problems carry over! Does this happen to any others and how do I solve it?? It seems like there is no way for me to open a microsoft powerpoint file without having problems! PDF works fine...

So when I look at powerpoint files in my dropbox using a computer, every looks fine. When I look at the same file on my ipad by opening dropbox, the formatting is all messed up again like I described. With this problem, I can't ever work with powerpoint files on my ipad...?? This is so inconvenient.