For some reason I had a users computer ask for Microsoft Journal viewer source files whenever a pdf file was launched. According to Lancaster University this is a known problem!
You need to install (or repair) Microsoft Journal Viewer 1.5 using a reliable method (explained below).
You can do this by downloading the viewer from Microsoft’s site:
1. download the viewer from: Microsoft’s download Journal Viewer site.
2. run it.
3. follow instructions
4. retry the Adobe Acrobat update.