Generate PDF preview images automatically?
There a plugin for that:

https://github.com/carnesmedia/pthumb

PThumb is a Craft plugin that generates thumbnail preview images for PDF documents. It's easy to drop into your templates, requires only the commmand-line version of ImageMagick (not the PHP bindings), and caches the generated thumbnails.

&lt;img src="{{ craft.PThumb.thumbnail(myAsset) }}"&gt;
&lt;img src="{{ craft.PThumb.thumbnail(myAsset, 100, 100) }}"&gt;
&lt;img src="{{ craft.PThumb.thumbnail(myAsset, 100, 150, true, 'jpg') }}"&gt;