The plugin toolbar appears on mousover on top of the page.
You can change the width of the content table by dragging the vertical line.
If you can't see any document, your Browser may miss the needed plugin for viewing .djvu (deja vu) files. Here you can download it: www.djvu.com/en/downloads
What's the heck is .djvu? ยป djvu.org/resources/whatisdjvu