Public Cloud storage services can be used as a document store to host a large number of documents. In many cases, the documents have to be encrypted in order to ensure their confidentiality, integrity and privacy. As the number of documents increases, searching for the desired documents over the encrypted dataset can be a difficult and resource intensive task. In this paper a novel ranked searchable encryption scheme has been presented, implemented and deployed on a public Cloud Service Provider. The scheme exploits the properties of modular inverse to generate a secure inverted index and a probabilistic trapdoor respectively. The probabilistic trapdoor helps in preserving the privacy while searching. The scheme is deployed on British Telecom's public Cloud offering and the efficiency of the algorithm is tested on a real-world dataset of documents. The performance analysis yields that our scheme not only provides a higher level of security but also lightweight.