I think India could conquer Pakistan, although not without a devastating nuclear exchange as the cost. But if it did, it wouldn't be able to govern it. The Pakistanis are probably the most heavily-armed citizens on the planet, and Indian troops would never be safe there.
I sympathize with the Indian position. The attacks in Kashmir are unacceptable. But if they're bad in Kashmir, just think what they'd be like if India occupied all or part of Pakistan itself.