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.
Store executed supplier PDFs and certificates under one envelope ID.
Keep signed supplier agreements and their signing proof together in the right supplier folder, so your team can find both when needed.
Check contract packet versions and flag missing files for correction.
Your requester sees exactly which contract files are missing, while the approval stays in correction for follow-up.