This plugin generates a thumbnail everytime you upload a PDF attachment. Generated thumbnail is an image of the first page in uploaded document.
This plugin hooks into the media manager and generates a thumbnail everytime a
PDF is uploaded. Generated thumbnail is an image of the first page in the
uploaded document and is named
PDFNAME is replaced
by uploaded document filename.
Generated thumbnails are equivalent to featured
images so that common thumbnail
get_post_thumbnail_id() can be used for PDF attachments. See
Post Thumbnails for information
on how you can use thumbnails efficiently.