I've got no say in what you link to, but that site is giving away free downloads to materials that are still covered by copyright. It's not that that practice is money out of my pocket, but it actually IS money out of my pocket...
Of course, you shouldn't look a gift horse in the mouth, but let me grumble a little. Why not preserve the original resolution of images in a PDF file with an OCR layer? It's not that difficult - I know it for sure, because I widely use OCR software.
Of course, the question of copyright comes up. But to be honest, bootleg scans of almost all Squadron-Signal books could be found on the Internet already 10-15 years ago. I do not provide links to illegal content, but everybody can easily found them if necessary.