I don’t have an answer as to why it was accessing documents, but this process is apparently something that is supposed to keep the wheels from falling off while Windows updates are being applied in the background. I’ve never noticed it running myself, but I do know from experience that things like driver failure or inexplicable hardware problems are often the herald of the ‘update and restart/update and shut down’ options appearing in my start menu. WaaSMedicAgent.exe is supposed to stop those problems happening when an update is being prepared.