See 4:30, there is a ladder that can be used to climb a pipe:

http://www.youtube.com/watch?v=jUl7biSQ9E8

As you can see here:

http://imgur.com/EhfV3bT

The ladder is not where it should be and I can't climb over the pipe.

Is there something I am missing?

Resolved with NoClip ... press N and go ...

Not for me, almost impossible task because ledge isn't shaped to up-collide with me too easily. Even harder is when you get ACRO bonus and can't go out from there. ;-)

I know this reply comes few years late but the ladder is supposed to be missing at least on hard difficulty level. It's an intentional trick jump you need to do. Here's a video of me doing it:

https://www.youtube.com/watch?v=In4wD2ZGazQ

Here's another video of it with better quality from someone else:

https://www.youtube.com/watch?v=Ee38M5BnIGk

People who don't want to do harder first-person platforming should select easier difficulty level. Patch 1.3 devs already made the ladders from easy difficulty part of the normal difficulty setting but kept the jump in hard difficulty which is a good thing.