Google Contacts, the address book built into Gmail, lets you keep track of all your contacts, see when you last interacted with them, and more.
Combine listed PDFs into one file for each ready 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.
Put requested report pages in order and send back one PDF link.
Your teammates get a combined report PDF in their requested page order, with a link back in the email thread.
Save files from the office inbox in the chosen archive folder.
Your email attachments land in the archive folder you choose, with their original filenames, ready for your team to find.
Find shared files coworkers request by topic or project.
Your coworkers get a file link on their request, even with only a topic or project. Unclear matches come back with a question.