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// For complete examples and data files, please go to https://github.com/groupdocs-metadata/GroupDocs.Metadata-for-.NET
// initialize Pdfformat
PdfFormat pdfFormat = new PdfFormat(Common.MapSourceFilePath(filePath));

// get pdf schema
PdfPackage pdfPackage = pdfFormat.XmpValues.Schemes.Pdf;

// update keywords
pdfPackage.Keywords = "literature, programming";

// update pdf version
pdfPackage.PdfVersion = "1.0";

// pdf:Producer could not be updated
//pdfPackage.Producer="";

//save output file...
pdfFormat.Save(Common.MapDestinationFilePath(filePath));