Could not see AWS LB classic X-Forwarded-For** header

Hello.

The document you shared belongs to ALB.
The classic load balancer documentation is below.
https://docs.aws.amazon.com/elasticloadbalancing/latest/classic/x-forwarded-headers.html

The X-Forwarded-For request header is automatically added and helps you identify the IP address of a client when you use an HTTP or HTTPS load balancer.

You can use the "X-Forwarded header" if the listener configuration is HTTP/HTTPS.
https://docs.aws.amazon.com/elasticloadbalancing/latest/classic/using-elb-listenerconfig-quickref.html

Configuration examples for Apache etc. can be found in the following documentation.
https://repost.aws/knowledge-center/elb-capture-client-ip-addresses