You can abort a work order in three ways:
right click on a work order and in the context menu and choose "Cancel" option;
in the detail preview, extend the "All actions" dropdown and select "Cancel"
in the work orders list choose all work orers you would like to cancel and do it simultaneously to multiple entries.
A work order may be canceled as long as it has not been started or completed. When you try to abort multiple work orders simultaneously and see that the "Cancel" option is not active, it means that the list contains a work order that cannot be aborted because of the reason mentioned above. In such a case you need to untick any "non applicable" items and try again.
A canceled work order may be edited, moved to archive or duplicated.
When you click "Cancel", you have to leave a comment on the reason for cancellation, which will be seen in the work orders history and confirm. As a result the employee will not be able to perform cancelled work order.