I will not be going through How to flash the Rom or something basics like that. This tutorial is just for solving the above mentioned problem. Let’s go through all the steps
1. Reboot in your recovery mode. Clockwordmod or something that you have installed.
2.Wipe data/factory reset, cache partition and dalvik cache.
3. Flash the PAC Rom.
4. Flash the Google apps.
5. Now flash the Android keyboard 4.2
After flashing reboot to your PAC ROM, and now you have to disable Android Keyboard (Aosp) so that you can use new flashed Android keyboard 4.2 .
Goto Settings > Apps > All > Android Keyboard > clear the cache and tab Stop & Disable
If you need you can go to Settings > Language and Input >and set Android keyboard 4.2 as default.
But I think if you disable Android Keyboard (Aosp) the system will automatically use new keyboard.
Hope it works for you all. It worked for me perfect.