PFDS

When choosing a life jacket for rafting, you can consider things like:

Size

The jacket should fit snugly around your torso, but not ride up when you raise your arms. It should also be based on your chest size, not your weight.
Type

The type of jacket you choose can depend on the type of rafting trip you're going on. For example, Type V jackets are more buoyant and durable, making them better for whitewater rafting. In contrast, Type III jackets allow for more movement and are better for leisure trips.
Buoyancy

Whitewater rafting jackets need more buoyancy to keep you afloat in fast currents, so they're often bulkier and have a high-cut front. The average adult needs 7–12 lbs of buoyancy to stay afloat, but your body mass index (BMI), lung size, and clothing can also affect your buoyancy.
Safety features

Some safety features to look for include a large collar for head support, waist ties, a safety strap between the legs, buckles, and reflective tape.
Comfort

The jacket should be comfortable and allow for unrestricted movement. You can test it in shallow water to see how it handles, and make sure it keeps your chin above water when you tilt your head back.
Visibility

The jacket's color can also be important, as some colors are more visible in certain conditions. For example, black jackets can get very hot in the summer, so you might choose a different color if you're rafting in hot desert rivers.

For another article about choosing a PFD, read this article by REI

What you need in your boat?