How many people have witnessed Earthrise?

24 people have gone around the Moon on nine Apollo missions (8, 10-17). 3 of those 24 were repeat visitors. I'm not sure if Apollo 13 saw the sight you describe, but all of the others surely did. Apollo 13 only had one chance, and they probably had other things on their minds at that time. Although according to the official transcript, someone said "That view out there is fantastic!" just after AOS (Page 410), so they probably did at least glance out the window at Earth Rise time.

I concentrate on Earthrises documented by Hasselblad images. The Apollo 8 earthrise image is part of the question.

An Apollo 10 CM photo AS10-27-3888 called Earthrise from lunar orbit.

Earthrise as seen from the Apollo 11 CM AS11-44-6547:

Another Apollo 11 image AS11-37-5441 taken from the LM:

So we got earthrise images from both the Apollo 11 LM and CM.

Apollo 12 LM image AS12-47-6885:

Apollo 13 did not enter into a full lunar orbit, they did no photos of an Earthrise.

From LM 14 in lunar orbit AS14-66-9228:

A very special Earthrise AS15-97-13268:

Earthrise with CSM seen from the LM AS16-113-18287:

The CM in the orientation shown could not see the Earth.

Apollo 17 CM with the docked LM AS17-151-23188:

The Earth is only visble to the astronauts in the CM but not in the LM of mission 17 when this image was taken.

So we got Earthrise images by every Apollo mission in full lunar orbits: 8, 10, 11, 12, 14, 15, 16, 17. But it is not documented if all astronauts took their chance to see it.

As PearsonArtPhoto wrote three astronauts did two missions.

All images from ALSJ NASA Apollo Lunar Surface Journal.