There are many free and commercial tools that read and allow you to modify the metadata of a document. The majority concentrate on digital images, audio and video data. However some tools can also access, delete or edit a document's metadata.
Exercise: Install and [[http://www.sno.phy.queensu.ca/~phil/exiftool/|Exiftool]] by Phil Harvey to see what kind of meta data is collected in your files.
[[File:metadata5.jpg|metadata 5]]