A computer-implemented online conferencing transactional platform system comprising an interaction module, a video-conferencing module, and a storage device may allow multiple participants in a video-conference to access, co-browse, collaboratively edit, and sign a transactional document. An interaction module fetches an image of a transactional document and a field identifier for an interactive transactional document element to be filled out from a remotely-connected secure signature API, and displays the image of the document, along with the interactive transactional document element on a webpage interface to a moderator and a signer end user in a video-conference. The interaction module receives a filled-out transactional document in an I-frame from the secure signature API, allowing the signer end user to sign the transactional document using a secure embedded signature process.