This message is displayed if you try to export results to an existing .pdf file from the command line. The fact is that you cannot export results to an existing file from the command line. To avoid this error, specify another file name that does not coincide with any existing .pdf file in the desired folder.
Note that if the specified file name corresponds to a non-existing directory or the file name is not specified at all (its value is an empty string), LoadComplete will create an appropriate file with the name that starts with aq in the <User Data>\Documents folder.