public static void ProtectDocument()
{
//Load an existing word file
WordFile wordFile = new WordFile();
WordDocument document = wordFile.Import(File.ReadAllBytes("Sample.docx"));
WordDocumentBuilder builder = new WordDocumentBuilder(document);
//Protect file with password and permission
builder.Protect("password", Protection.ProtectionMode.AllowComments);
File.WriteAllBytes("Protected.docx", wordFile.Export(document));
}