One huge advantage of ImageMagick (IMHO) is that it can make images out of PDFs. Many clients want thumbnails of their pdfs so that they can link to that.
So, I rather naively told File.php that .pdf files were Images, hoping that a thumbnail would just be created. Doh!
But I did copy a pdf as a png (ludicrous I know) and lo and behold the system made a thumb out of it and it worked.
I am therefore suggesting that if a pdf is uploaded, the upload system is arranged to make a png or jpg copy of the pdf and store that as well so it can be used for link purposes. I think this would a a popular idea. I will try to present an example myself.