Sorry, the URL we are using is for our application, which is not public. We finally found out the reason is that, when opening the pdf file in the IE browser, the "div" value in the jsp file becomes null, instead of 100%, that's why the pdf file is not open in 100% mode.
We fixed it by specify the value "100%" to div in our jsp explicitly, and then the pdf can be viewed correctly.
Therefore, it should not be a PDF problem...
Thanks all the same!