Originally Posted by JohnGalt
I noticed the same thing. I'm not satisfied with my solution, but I have made these files visible by reducing the zoom factor. On most of the Archive.org PDFs, you can view them at 150% okay, but 100% seems to be always safe for me. When you zoom in too much, it becomes an essentially blank page.
There is also a lot quicker way to convert djvu's to pdf using free djview viewer, but ocr layer will be lost.
It took me about 5 minutes on my slow laptop to convert(export) above mentioned (hiddenchurchofho00waituoft 746 pages 22 MB) djvu to pdf at 150 ppi and 75% jpeg.
created pdf is 5x bigger, 110 MB, but easily readable on e-readers and tablets.