We have had some experience with difficulty displaying PDF files using a combination of Windows 7 and Internet Explorer 8. Adobe has addressed a host of compatibility issues related to this difficulty. Solutions for displaying PDF files using Adobe Acrobat in an Internet Browser are listed on a web page on the Adobe web site entitled "Can't view PDF on the web".

Here is a link to Acrobat configuration help at adobe.com. We have found that step 5 appears to help. If it doesn't, then step 5 under More Solutions appears to help as well.