Google Drive is Google's file sync app that lets you store all of your files online alongside your Google Docs documents, and keep them synced with all of your devices.
Combine transaction documents in order and message the PDF link.
Get PDFs merged in the order you list. The folder owner gets a link in chat. You choose where the finished file goes.
Pair executed deal agreements with their signing history.
Keep signed agreements ready for handoff, with signature certificates or audit trails beside them and a clear note when proof is missing.