documents for converting a leasehold property to freehold

What are the important documents for converting a leasehold property to freehold?
In a freehold property, the owner can enjoy the absolute ownership but in a leasehold property, the holder of property is a lessee and the owner of the property is a lessor who leased out the property for a certain period of time and after expiry of the lease term the lessee has to vacate […]