A famous feature of Rhythm Knowledge is the use of randomization to test true limb independence.
Let’s say you find a PDF. Now what? Most drummers quit after 10 minutes because they try to play everything at 200bpm. Here is Mangini’s actual study method (revealed in a 2022 interview with Modern Drummer):
This is the most "leaked" page of the RK method. A PDF would show four bars of 4/4. The top staff shows quarter notes (4/4). The bottom staff shows a dotted half-note triplet (3 over 4).
A real RK PDF has four pages of charts walking you through the math of this shift.