Attach Document to the PO after approval or approval is in progress.

Summary

Is there an option to attach the document to the PO while approval is in progress or after PO approved.

Content

Hi All -

Is there an option to attach the document to the PO while approval is in progress or after PO approved. 
Here is the business scenario: 
1) Buyer who creates the PO will attach contract kind of document in the attachement section which needs to be reviewed by approver. 
2) when approver receives the notification, he/she will look at the PO and download attachment and review. In case, if anything needs to be corrected, is there an option for him / her to attach the document to the PO. If not, he /she can forward the revised document to the buyer by email, but can it be uploaded to the PO after approval without withdraw the PO .