Win8/IE11: inline PDF rendering/page refresh issues when using scrollbar

I have an aspx page with 3 PDF pages embedded w/ iframe tags.

  <iframe src="pdf/BS351.pdf" style="width: 843px; height: 400px;" frameborder="0" scrolling="no"></iframe>

etc.  The PDFs are rendered correctly on page load, however when I use the page scrollbar (not the Adobe reader scrollbar), I see display not getting refreshed correctly.  I have included a couple of screenshots to clarify:

On page load:

When using scrollbar to the right to scroll down the page:

This behavior is not seen in other browsers or in IE8, 9 or 10.

Are there any changes in IE11 that may be causing this behavior?

Thanks

SG