Merging or Assemble SAP PDF forms

Hello Gurus,

I have a requirement to group all invoice forms to a single PDF.I went through the SAP program FP_CHECK_BATCH_PDF_RETURN for grouping documents.

In my case the business want to use tcode : VF31 for printing. I am using sap standard driver program : SD_INVOICE_PRINT01 for printing invoices.

What are the solutions available as I am really struggling to start.

Thanks.