OneDrive, Microsoft's file sync app formerly known as SkyDrive, lets you store your files online, edit Office documents in the free Office Web Apps, and easily access your online files from your PC.
Store signed supplier terms with the completion certificate.
Keep signed supplier agreements and their signing proof together in the right supplier folder, so your team can find both when needed.
List missing supplier contract files on the original approval request.
Your requester sees exactly which contract files are missing, while the approval stays in correction for follow-up.