Forensic watermarking is a tool for secure transmission of forensic questioned documents. The reported cases of fraudulent manipulation of forensic case documents are basic motivation behind the application proposed in this paper. Earlier approaches in forensic watermarking embed watermark onto whole document which is highly susceptible to attack. We have proposed a RROI based forensic watermarking of case documents which basically represents the rectangular region of a document (fingerprint/signature) that needs to be watermarked. In this, DCT and DWT based transform domain watermarking techniques were implemented on RROI and the performance of the two were compared on the basis of PSNR. Moreover, some attacks like scaling and addition of noise have been performed to check the robustness of the watermark.