Saving a new attachment consists of two processes: getting an annotation ID for the user and posting the attachment form.
Get attachment ID for user This API call gets the attachment (annotation) ID for a user of a given type, which is required before a new attachment can be saved.
Post attachment form This API calls posts the attachment form, saving a new attachment. Before the call can be made, the annotation ID for the new attachment must be generated with the Get annotation ID for user API call.