Should you walk backwards while marshalling an aircraft? Any references?

Individuals need to be taught where to stand when directing aircraft so they will not have to move backward.  One of the Flight Line Marshaller’s responsibilities is to be responsible for the safety of assistants and trainees by verifying they know where to stand when directing aircraft, so they will not have to move backward.

See below from Aircrew & Flightline Tasks

O-3001   Discuss Flight Line Marshaller’s Responsibilities

2. You are responsible for the safety of your assistants and trainees, assuring they are properly trained
a. Verify they know where to stand when directing aircraft, so they will not have to move backward.
b. Verify they know the proper hand and arm signals to direct the aircraft.
c. Verify that they know how to communicate with you and you with the Flight Line Supervisor for instructions.

Also see suggested marshaller positioning below from  Aircrew & Flightline Tasks

O-3009  Perform Aircraft Taxi Procedures

2. CAP personnel marshalling aircraft must position themselves to meet the following requirements.
a. Never position yourself in the path of an oncoming aircraft
b. Never position yourself in a location where any part of an aircraft will pass over you
c. Never walk backwards on the ramp
d. Never run on the ramp
e. Always marshal aircraft entering a congested ramp under CAP control
f. Always get enough personnel to control aircraft movement without compromising safety
g. Always position yourself where you can maintain direct eye contact with the pilot-in-command (ten feet to the
pilot’s left of the left wing tip and far enough in front of the aircraft to allow for a turn in front of you is ideal)
h. Always hand the aircraft off to the next marshaller before the pilot losses sight of you.
3. Careful planning of the number of resources and their position can accomplish this with ease. Suggested marshaller positioning is shown on the following diagrams for departing (fig. 1) and arriving (fig. 2) aircraft.

You can also take the "Aircraft Ground Handling" Course on Learning Management System to learn more about aircraft movement.  You can access the course via the following link:  Aircraft Ground Handling