To complete the purchase of an apartment at Prestige Raintree Park, several essential documents must be signed. These include the Booking Form, Sale Agreement, Allotment Letter, Builder-Buyer Agreement, Possession Letter, Occupancy Certificate (OC), Khata Certificate, and No Objection Certificate (NOC). It is crucial for buyers to carefully review and understand the terms outlined in these documents and seek professional advice if needed before signing. Keeping copies of all signed documents is recommended for future reference.