Why can't you just average ADC samples to get more resolution from an ADC?
If you ask someone to measure a 45.2cm board accurate to the nearest centimeter, they would (or should) answer 45.  If you ask then to measure it again, they would answer 45 again.  Repeat the exercise 8 more times and the average of all the measurements should be exactly 45.  No matter how many times one samples the input, one will end up with a value of 45.  The average of all those readings would, of course, be 45 (even though the board is 45.2cm long).

If you had the person adjust the measuring apparatus so as to read 0.45cm long before the first measurement, 0.35cm long before the second, 0.05 cm long before the fifth, 0.05cm short before the sixth, etc. up to 0.45cm short before the tenth, then two of the measurements would read 46 and the other eight would read 45.  The average of all of them would be 45.2.

In practice, managing to bias things so precisely is difficult.  If one randomly adjusts the measurement apparatus before each measurement to read somewhere between 0.5cm long and 0.5cm short, then about 1/5 of the measurements would read 46 and the rest 45, but because the adjustments are random the actual fraction might be higher or lower.  Taking ten measurements would not add quite a full significant figure worth of precision, but averaging about 100 would.

I'm not sure I quite understand the paper's rationale for the distinction between averaging and right shifting.  One needs to be mindful that the apparent precision achieved by averaging may exceed the meaningful level of precision, but from my experience the question of when and how much to right-shift should be driven by the limits of the processor's numerical range.  Working with numbers that are scaled up as much as they can be without causing overflow will generally minimize the effects of rounding errors, provided that one doesn't attach undue significance to small amounts of noise.

Incidentally, in the original usage, to "decimate" an army was to kill 1/10 of the soldiers therein.  To decimate the data from an ADC is to discard part of it.  The common prefix with the phrase "decimal point" does not imply an association.