Need process steps to customize ISupplier Portal order page to add new button to display custom temp

Problem Description: Try to add new button to display custom templete but facing lot of difficulties. The custom template pdf file is available in FND_LOBS standard table. need to pick up this custom pdf file and show when we click on new button.

Nagivation path: 11i ->ISupplier Portal Full Access -> Orders tab -> Select any PO -> Click on 'NEW BUTTON' - it should show the custome templage that is there in FND_LOBS standard table.

Please let us know the customization process steps to impliment above changes.

OA Framework Version 11.5.10.6RUP
MDS Version 9.0.5.4.89 (build 560)
UIX Version 2.2.24.2