Do .pdf have a image thumbnail, or a preview?

[evilaro]

Hello

I wonder if .pdf files have a small imagen inside the file
that I could look..

And how to extract it...

Thanks

Emilio
PS
I have seen that you could extract the images from the .pdf, which is good
but I really meant to extract the image representation of the
.df, in another words, the imagen that will represent the .df document
maybe the first page...  I hope it exists.