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 report pages in order and link the finished PDF to its request.
Your report or invoice packet is ready on the same spreadsheet row as the source PDFs, with its pages in the order you chose.
Combine report PDFs in the requested order for review.
Your reports or invoices become a single PDF in your shared folder, with a link on the request you submitted.