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Apparently you can use  DSOfile for Open XML documents, but at least for me there were problems in x64 environments:

In this 64-bit environment, DSOFile.dll can successfully read properties from Office 2003 documents (eg. DOC), but in the case of Office 2007 documents (eg. DOCX), only empty strings are returned for all properties, or else an error is generated. – Stackoverflow ,http://stackoverflow.com/questions/1926482/unable-to-read-office-2007-doc-props-using-x86-dsofile-dll-on-x64-system

So - use the  Open XML SDK 2.0 for Microsoft Office. After downloading and referencing the dll:

using DocumentFormat.OpenXml.Packaging;
WordprocessingDocument document = WordprocessingDocument.Open(filePath, false);
PackageProperties standardProperties = document.PackageProperties;
CoreFilePropertiesPart fileProperties = document.CoreFilePropertiesPart;
ExtendedFilePropertiesPart extendedPropertiesContainer = document.ExtendedFilePropertiesPart;

if (extendedPropertiesContainer != null)
{
    var extendedProperties = extendedPropertiesContainer.Properties;
}

var customPropertiesContainer = document.CustomFilePropertiesPart;
if (customPropertiesContainer != null)
{
    var customProperties = customPropertiesContainer.Properties;
}