This application is designed to facilitate secure and efficient digital signatures and validation of PDF documents, simplifying the way users manage electronic documentation. Built with robust encryption and authentication protocols, this application ensures document integrity and authenticity, making it ideal for STS users who need a reliable document security solution. The app allows users to apply legally binding digital signatures to PDF documents, reducing the need for physical signatures while ensuring compliance with digital signature laws and standards such as eIDAS. Each signature is encrypted and stored in the document, preventing unauthorized changes and ensuring that the signature remains secure and verifiable. In addition to signing capabilities, the application provides document validation tools, allowing users to verify the origin and integrity of any signed PDF. This is especially useful for managing contracts, financial transactions, legal documents and other sensitive documents that require high security. The validation process includes checks for spoofing, verifying signature authenticity, and detecting expired or revoked certificates.