LockDoc is a Chrome add-on designed for secure file sharing through Gmail. This tool allows users to send and receive encrypted files with ease, ensuring that sensitive information remains private. Users can simply upload files using the 'Upload' button in the Gmail compose window, which generates a download link for the encrypted files. Recipients only need a passphrase to access the files, which can be shared manually or automatically by LockDoc, enhancing convenience while maintaining security.

The service does not require recipients to create an account, as they can download files directly after entering the provided passphrase. LockDoc also offers a log history feature to track sent files. With flexible pricing options catering to different user needs, including à la carte purchases and subscription plans with varying storage limits, LockDoc is an efficient solution for anyone looking to exceed Gmail's file limits while ensuring encryption.