As others have said this seems to be an issue with the way the Adobe Acrobat program handles the preview pane. As such I'm not entirely sure that this is a Microsoft bug, or an Adobe bug. I'm inclined to think this is an issue with Adobe.
I found a work around. Install the freeware program "PDF Previewer for Windows 8" and let it become the default PDF program, then go into "Default Programs" in Windows 8 and set Adobe Acrobat as the default again. This seems to leave the PDF previewer
program as the program that handles the preview pane while still leaving Adobe as the default program when you open a PDF.
I have done this on 2 machines, and will probably roll it out to all my Windows 8 machines if I don't run into any further problems. The link to the download is below.
http://www.windows8pdf.com/pdfpreviewer.html