Combine digitally signed documents (don't care about preserving signature)

** Overview

I have a use case where I have several digitally signed invoices. Each invoice is a separate PDF file. When paying these invoices we put together a "payment pack", which is basically all of the invoices were paying combined into a single PDF file, accompanied by a cover sheet with a payment summary. That payment pack is then circulated to signatories to be signed via Adobe Sign, authorising the vendor payment.

** Problem

When I try to combine digitally signed PDFs in Acrobat, it removes all of the digital signatures from the invoices except for one. The problem this causes is that the person combining the PDFs together is left with a digital signature placeholder field that they don't know how to remove from the PDF.

Because I truly don't care about preserving the validity of the original digital signatures on the individual invocie PDF files, a very acceptable outcome would be a combined PDF with all of the digital signatures removed. 

There are more than a dozen people each performing this same action a dozen or more times a day. I was hoping for an easy way I can teach all of them that is straightforward and easily understood.

** Question(s)

1. Is there a way we can combine all of the PDF together but keep the original signature (i.e. the graphic NOT the certified digital signature)?
2. If #1 is not possible, is there a way we can combine all of the PDFs together and totally remove all of the digital signatures?