To do this you need to edit what is shown in the printout of this document. Click on the Mgeaventory logo and select Document Templates and View Document Templates from the menu on the left.
Once there, select the Document Teplate you want to edit, for example, "Sales Order".
From the screenshot below you can see in this example that certain SKUs are ticked which means that it is shown in the printout:
In your case, if this option is not selected, you need to open the document you want to edit and tick the box next to "SKU". And don't forget to click "Update" to save your work!
Or login to your account.