HOW TO SELECT A BUNCH OF LAYERS AND TURN ON OFF ON MY ACROBAT, VERSION XI PRO.

You can turn the layer visibility on and off from the layers panel, it looks like a pancake icon. (turn the eyeball off or on). You can also use a preflight profile to turn specifically named layers on and off, or delete the unwanted layers. Make a duplicate of an existing profile (Tools> Print Production> Preflight> Profiles, fly-out menu) You can't edit an existing profile, but you can edit a copy. You can make as many profiles as needed to turn off (or on) as many layers as you like and combine them into one action using the Action Wizard.

This is a bit off-topic, but you can also add buttons to show/hide layers.

Note, not all PDF viewers respect layer properties, so PDFs should be viewed in Acrobat or Reader.