I have a full Standard version of Adobe Acrobat version X on my computer. Today I suddenly lost all previews of my pdf docs in DO. any suggestions on how to get my views of PDF docs back?
Try (re)installing a PDF Viewer which includes a preview handler, e.g. Acrobat Reader or the PDF-XChange viewer.
I'm not sure that Acrobat includes a viewer, but you can install Acrobat Reader on the same machine.