A number of people have had problems with displaying the Adobe Toolbar in Internet Explorer 8 after upgrading to Adobe Reader 10 (X).
After a little digging on forums and finding no real answer I had a lateral think and found the problem.
You need to fix this in the Adobe Reader software NOT in IE8.
- Open up Adobe Reader.
- Go to Edit – Preferences
- Click on Internet
- Remove the Tick from the Display in Read Mode by Default box
You should now find that the toolbar is back when you open a PDF in IE8.
Hope this works for you – it did for me.