Add custom field from SO to Packages and Invoices?

Add custom field from SO to Packages and Invoices?

Is there a way i can add a custom field that I have in the Sales Order module to Packages and Invoices? There are a few fields that I would like to be able to see throughout the whole process. 

Or is there a way I could create a custom function/field update to create a separate field and have it updated when the package and invoice are created?