Threre might be one more reason for this message. If a number range for EDIDOC object is incorrect in remote system and there are some existing entries in EDIDC table under IDOC number this will show you the same error.
If this is just after client copy transfer NRIV table as well and reset number range buffer used or restart application server. By default EDIDOC cache is 1000 entries you may check current number by SE37->NUMBER_GET_NEXT and compare with EDIDC table. If it is incorrect but in SNRO is already fixed go to SM56 and use goto->reset buffer.
regards