"Back focus" is a general term a little too broadly used for "when the camera focuses on THIS what is actually in focus is THAT"
You don't need a PDF.
- Find a ruler
- Put in on a table so that one end of it it pointing directly at you.
- Open the lens aperture all the way up (smallest f-number)
- get down fairly low so so the edges of the ruler are receding away from you like railroad tracks receding into the distance
- focus on a point half way down the ruler. The 6 inch mark, say. Be careful about what you are focusing on.
- Click.
now pixel peep to see what, exactly is actually in focus. Is it the 5-3/4 inch mark? Is it the 7 inch mark? Let's hope not! Let's hope that it's the 6 inch mark!