I've disabled both the Adobe Reader Add-on and the Adobe PDF Link Helper to force IE 8 to open PDF's outside of the browser i.e in the stand alone reader application.
After doing this I did some testing, a google search for "test pdf" produces numerous direct links to pdf files. If i click any of them it causes IE to display the message bar "Internet Explorer blocked this from downloading files to your computer, click her for options.." When I click on the message bar, it appears to download the file , then nothing happens. Next time I click the link it opens in the stand alone reader just fine and so do all PDF files, until the browser is restarted or a new tab is started.
This only seems to happen in IE8. IE9 doesn't have the problem.
If I open a web page that has a link to a PDF that always work.
Help? I can't roll this out to prod. Users will get very confused...
