This free application note summarizes precisely where PDF creators should add XMP metadata to PDF 2.0 objects, and thus where PDF 2.0 processors should search for it.
Metadata has been described as the business card of a particular digital document. Metadata often comprises a set of properties, where each property has specific meaning in the context of the document, such as the title and creator of a PDF document or the GPS position where an image was taken.
In document processing, nothing works without meaningful metadata at least not if you want to automate it. The XMP format is key.
I am proud to say that IDRsolutions has joined the PDF Association. I think it an association that you should also consider joining.