PO Modification only print the line changed in the pdf embeded in modification email

[sigwork]

Hi
We are trying to reove message sending on delivery completed for POs.

We first went to SPRO : Materials Management > Purchasing > Messages > Fields relevant to printouts of changes and deselect PO column

We then had to come to SPRO and add
Materials Management > Purchasing > Messages > Output Control > Message type > define message type for purchase order > Maintain Message Types for PO
We have set Program to FM06AEND and FORM routine to CHANGE_FLAG.

It seems to wok but now when we change a line (material) in the PO, instead of receiving the whole new PO attached as PDF, the PDF only contains the line changed.

Do you know where this could come from ? Or do you know what is the abap program called to generate the PO PDF ?

Thanks