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 bid PDFs in the listed order and send the proposal link.
Get PDFs merged in the order you list. The folder owner gets a link in chat. You choose where the finished file goes.
Combine bid sections into one PDF for proposal review.
Your reviewer gets a single PDF in the order you set, with the finished packet attached and linked on the project task.