That might be true, but these ones are not. I can't efficiently read them on my smartphone and have to scroll around a lot. They also show two pages on one, probably to be better printable for some marketing material, but I would never want to print a PDF that's mostly black, because that would overwhelm my printer. I'm also not near a printer right now. This is clearly inaccessible to me.
HTML, on the other side, can be easily made readable on any device. Even if the author didn't care, through readable mode in my browser.
PDFs are often the BEST way to read something. I prefer PDF text books over any other format, because (not very good) computer algorithms laying out text is inferior to proper professional layout.
HTML, on the other side, can be easily made readable on any device. Even if the author didn't care, through readable mode in my browser.