DocxFormatProvider provider = new DocxFormatProvider();
using (Stream input = File.OpenRead("InputFile.docx"))
{
RadFlowDocument document = provider.Import(input);
RadFlowDocumentEditor editor = new RadFlowDocumentEditor(document);
Run firstRun = document.EnumerateChildrenOfType<Run>().First();
editor.MoveToInlineEnd(firstRun);
editor.InsertText("Hello word!");
//DocxFormatProvider provider = new DocxFormatProvider();
using (Stream output = File.OpenWrite("F:/POCForSOW/ConsoleApplication1/ConsoleApplication1/Sample.docx"))
{
//RadFlowDocument document = CreateRadFlowDocument();
provider.Export(document, output);
}