It was observed that unit’s column was not populating on advance pdf template, as the column is missing in invoice record.
Further analyzing the issue, it was found that it was rooted because of the invoice form’s type. So, even though the column/field is visible in the form and enabled to expose in the form level, in accounting or finance related invoice forms the Unit column doesn’t show up in the record.
Hence to resolve this we can create a custom transaction line fields in those concerned forms and can source the unit values from item record. This can be fetched from the Advanced pdf prints.