Hi Kesannah,
now and again you'll find documentation for downloading which is in PDF format i.e the filename ends in .pdf
PDF is just one of many attempts to save files in a format which everybody can read.
This is the main reason why you (may) need Adobe, as it's a PDF reader program.
It's a free program, BUT ... as Michael says, it's very bloated, and I also recommend and use the free Foxit program. The documents load extremely fast, and you don't get the annoying pop-up from Adobe asking you constantly whether you want to load the latest updates.
So it is handy to download Foxit when you have a bit of spare time, and then it is simply there, anytime you need to read a PDF document.
Bob