Attaching a document while adding a comment during a workflow transition

There was a request from a potential client about attaching scanned documents as a comment while doing workflow transition. This feature could be incorporated, especially useful for engineering companies, where supervisors give comments to Autocad drawings. Since there is no way to directly annotate a autocad drawing in Mayan, the only option is to upload a annotated file done on desktop as a comment while making a workflow transition.