Didier,
my approach would be to
*) store the document in a BLOB-field of a database table. There you can keep track of the reviewing process by setting status fields.
*) In the filesystem (preferably on the fileserver) you can have a picture all in white where it says *DRAFT* in some fancy way.
*) if the status of the document not equals *approved* then ...
paint the draft-image as watermark
This is done by having a TImage on your form, loading the desired image into the TImage, use the OnPaintWatermark procedure of the TWPRichText in the following way:
my TImage is called img1...
WPPrintTiledBackground(toCanvas, PageRect, img1.Picture.Graphic, XRes / WPScreenPixelsPerInch);
Hope that helps