Hi Thomas,
Yeah do check with the wflow consultant and for the request pending for approval you cannot approve from your end.
Either mass approval can be done by the approver or download the documents which are pending for approval by taking a report using the transaction PTARQ.
Then directly update the 2001 infotype through lsmw. But this is complex if the record size is huge the other option would be better ask everyone to go ahead with mass approval then post the documents.
Regards,
Mithun K