Originally Posted by CAZORLA
no its not enabled as my phone has not been rooted
As goofball2k said, you don't need to root your device to enable USB debugging. In your case though, you can't enable it due to the broken screen.
When your screen is locked and you connect your phone to the pc, does it show the phone? If it does it will probably show no folders inside. Right?
What you need to do is unlock the bootloader, flash a custom recovery and then in the recovery you will be able to use adb pull command.
To do all that you can read efrant's guide (unlock bootloader, flash custom recovery) in this forum, or you can use a toolkit like this guy in your same situation: http://forum.xda-developers.com/show....php?t=2177440
I would recommend efrant's guide as it teaches you the basics on how to use adb and fastboot to flash anything you like.
Sent from my Nexus 4 using xda app-developers app