Checks the PDF for missing file identifiers in the document metadata, for example: VersionID, DocumentID or RenditionClass.
XMP metadata is descriptive information about the file embedded in the PDF, for example the name of the author, keywords, copyright information... XMP refers to labeling technology that is used, i.e. Adobe's Extensible Metadata Platform. You can view the XMP metadata in a file's Document Properties in Acrobat (Click the Additional Metadata button, then select Advanced).