What IDoc specifically?
Unless Sales Org is in the IDoc control record EDIDC, such transaction would have very bad performance because we can't easily select the data from the segments.
Actually allowing "external partners" direct access into your SAP system is not a great idea either. What exactly are you trying to achieve with this? Isn't there a better solution that would not involve someone logging into SAP and digging around in the IDocs? Can't you have the IDoc send a confirmation back to the partner or something like that?