Where/how does the Magic: the Gathering Quick Start Guide booklet actually get distributed in the physical world?
I can confirm that these kind of booklets were available up to at least 8th Edition as physical copies: I bought some kind of introduction pack which contained two 40 card theme decks and a quick start guide (see archive.wizards.com, it's the rulebook that's available as a PDF).

So far it doesn't look like they're still available as physical copies. My first guess was to look at the Magic 2015 Core Set 'Deck Builder's Toolkit' because according to the Wizards website it contains:


  The support you need to build your own Magic: The Gathering decks. Includes 125 semi-randomized cards suitable for building several different decks, four 15-card booster packs from a variety of recent Magic sets, 100 basic land cards, a deck builder’s guide, a Magic learn-to-play guide, and a card box. (Emphasis mine.)


However, a youtube video (I will link in the first comment, since I don't have enough reputation for more than two links) shows that it's the same 'Rules Reference Booklet' as mentioned in the question, as well as a 'Deck Builder's Toolkit' fold out which I think contains deck building tips. Clash Packs seem to contain similar kind of fold outs (see second video linked in comments). Together with Jefromi's answer it seems unlikely that this rule book is physically available anywhere else.