Useful if the PDFs are custom-sized to eBook device sizes. If they aren't, they are tenable only for Kindle DX and Digital Reader owners.
And indeed they aren't. They do not seem to be generated by the website--whose URL by the way is http://worldebookfair.com/
. In fact, I have the impression that this website is simply a database built by a spider that indexes PDF documents at a variety of electronic libraries around the world... and perhaps mirrors them.