Hello,
We were able to reproduce it, but it still seems like documentType is returning 'pdf' even when loaded in ie9.
To clarify, ie9 does not support direct pdf viewing. By design, you need convert it to xod.
In your first post, you've mentioned "For IE9 (pdfnetjs not supported) we request server to convert file to XOD for webviewer."
However, your sample doesn't appear to be converting to xod.