Documentation/Tutorial Creation Software

I want to create some tutorials for my software class. I remember seeing some software for the mac that is excellent for the job. I can't remember what the name of the software is.

The software is as follows:
- You take some screenshots of various stages of using the software
- You then add text in the software
- You can then create a tutorial out of it

Anyone have any ideas what it's called?

Thanks

 

By tutorial I mean a step by step instructional pdf that kids can download from the school system and follow.

The app that I remember gave you the ability to create screenshots one after the other using a hotkey. You can drag and select a portion of the screen. You then add instructions to each step.

I know this is really vague and I'm sorry but I remember seeing a demo of it somewhere online.

Thanks for trying to help everyone.

Edit:

I've found it. It's only taken me two weeks. Sorry for not being clear enough but after countless google searches and tryign different word I finally got it:

http://www.bluemangolearning.com/screensteps/

Thank you to everyone who tried to help