Hello
You are on right track by referring to SAP Program FP_CHECK_BATCH_PDF_RETURN
How to assemble PDF form pages into one file - ABAP Development - SCN Wiki
Run report FP_CHECK_BATCH_PDF_RETURN with following
- Bundle Mode: M
- All forms in one pdf - Checkbox ticked
In Program SD_INVOICE_PRINT01, refer to line no 280 and 305. Looks like this program already caters for bundling. All you need is to find where the MEMORY ID ' BUNDLING' is set.
Regards
Sandy