Documents verification on purchase from builder

I have purchased a leased property from builder in karachi. On final payment, i have been handed following docs:

1) plot allocation
2) possession letter (stamp by builder)
3) copies of sub lease deed. They'll hand over the final original leased docs. On final payment
4) declaration letter

All of the above said documents are printed on my name. Can you please confirm how can i verify them ? Are these documents sufficient for purchase property ?