Get pages and iMovies free
You can check the app store in the purchased section to see if the apps are there, normally if you're using a brand new mac you should be able to find them there. If you bought a second hand mac I don't think you'll be able to get them for free (legally). 

There is something i tried a long time ago i'm not sure it's still working, you need to download the iWork ’09 trial Install it, open all of the apps (pages,numbers and keynote), quit the apps, launch the appstore and then update them.

I have no idea how to get iMovies for free.