OK for reading, no good for analysing
PDF has one major problem - no document structural markup, ie anything indicating what's a heading, where a paragraph starts and ends etc.
Fine for viewing on screen and printing, but if you want a machine to read it, analyse it, extract information for search & discovery, then it's awful. Even worse if you want to extract tables or other structured information.
HTML's actually a much better format for this.
Unfortunately a lot of documents are getting published (and archived) in PDF only.