Adding a Barcode to Invoices, Package Slips

Adding a Barcode to Invoices, Package Slips


It would be good if we could add a custom field to print on Invoices and Package Slips that allow us to print a barcode.

With our current ERP we have set it up so that it prints a barcode on the Invoices/Package Slips so that we can scan it into our Fedex machine and it automatically brings up all the shipping details on the Fedex machine.  

Here's and example: