I have just read the training material for a couple of the AX certifications. I didn't want to print it, so I tried to read it directly off my laptop, which with Adobe Reader is a completely disaster. It is completely unpredictable when the reader changes pages while scrolling the document and after reading very few pages you just get tired. I moved the material to my Mac which has a good PDF reader.
Today I found this free reader, which allows me to read PDF's proper on the PC: