After getting the gist from that video and from personal experience freelancing, I would say the major pain points for freelancers are:

a) Clients being slow on delivery of requirements/content but once they deliver it, they want things done urgently

b) Clients being slow to sign off stuff after delivery

c) Late payments after a lot of chasing

Documentation and NDAs can vary from client to client and is usually initiated from their side.

These are my experiences, others may have a different perspective.