Why is Quartus Prime Documentation splitted into 16 several .PDF files that must be downloaded seperately?

The separate user guides make it easier to see information for a particular aspect of using the software. I also find it a bit easier to search for something specific in the user guide I need to use for what I'm working on. There are plenty of hyperlinks between the user guides where needed, so you don't need a single monolithic guide as much any more.

Don't forget there's also the built-in help in the software.

#iwork4intel