Hi Wanangwa,
To add a thumbnail to an existing item, you'll need to upload it as a bitstream under the Thumbnail bundle (See
Edit Bitstream documentation). Is there a particular step in there that has not been working?
Alternatively if you need to auto-generate thumbnails for many existing items, you could look into the
media filters script. There are several filters for creating thumbnails based on PDFs.
Last, there is not currently a PDF viewer integrated with DSpace. There is an implementation that is
under review, and could theoretically become a part of the 10.0 release (but that is still unknown, not guaranteed).
Hope that helps you get started,
-Lia