It is possible to make changes in not yet fully approved documents after they were published to ApprovalMax by Dext.
This is how it works
In Dext, go to Costs -> Archive and click on the document that you want to adapt, then make your changes:
Next, click on Unarchive -> Clear publishing data:
Open the inbox and publish the amended document again.
Now, the changed document gets published anew to ApprovalMax and the approval process will restart.