The issue of the quality of the illustrations inside the PDF is always something that depends on the usage, would be nice to have the light version (I guess this is the one) for mobile devices and tablets that can move better a light PDF. But also having the option of a full PDF with some top quality images to enjoy when you check the document on your computer or bigger lcd screen.
The second issue is the index without hyperlinks and adding links to certain terms would be a nice touch to speed document navigation. Hope it is added in the future revisions of the document.