Thumbnail images not being rendered?

Installed the plugin and in general it works fine however it doesn’t appear to be showing thumbnail images of the first page of each document uploaded. It does show a pdf icon but not an image of the first page.

I understood the plugin was able to render images taken from each document uploaded but that this depends on the server?

At the moment I have my development site on my local machine using MAMP but also on a web facing server. The images are not rendering on either platform.

Apparently there are a couple of scripts that need to be present on the server for this function to work? Can anyone give me more details about that? It’s essential that I get the first page of each document rendered as a thumbnail.

Thanks