How can I unload the xps file in document viewer

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C#

XPS

DocumentViewer

I have a word doc/rtf file and got some code that it will convert to it xps doc and It can be loaded in the DocumentViewer, I have a button that will open the file in ms word so it can be edited and saved. The problem is since the xps file is open in documentviewer, I was not able to reload the xps document in document viewer. Can some help me unloading file in document viewer. Below is my code.

private XpsDocument ConvertWordDocToXPSDoc(string wordDocName, string xpsDocName)
		{

			// Create a WordApplication and add Document to it
			Microsoft.Office.Interop.Word.Application
				wordApplication = new Microsoft.Office.Interop.Word.Application();
			wordApplication.Documents.Add(wordDocName);

			Document doc = wordApplication.ActiveDocument;			
			try
			{
				doc.SaveAs(xpsDocName, WdSaveFormat.wdFormatXPS);
				wordApplication.Quit();
				XpsDocument xpsDoc = new XpsDocument(xpsDocName, FileAccess.ReadWrite);
				return xpsDoc;
			}
			catch (Exception exp)
			{
				string str = exp.Message;
			}
			return null;
		}

		private void LoadMyreminder()
		{
			string XPSMyReminder = String.Concat(Path.GetDirectoryName(_myReminder), "\\",
						   Path.GetFileNameWithoutExtension(_myReminder), ".xps");
			myRemviewer.Document = ConvertWordDocToXPSDoc(
				_myReminder,
				XPSMyReminder).GetFixedDocumentSequence();
			
		}

		private void BtnEditMyrem_Click(object sender, RoutedEventArgs e)
		{
			Microsoft.Office.Interop.Word.Application ap = new Microsoft.Office.Interop.Word.Application
			{
				Visible = true
			};
			Document document = ap.Documents.Open(_myReminder);

		}

What I have tried:

searching google, try to close the doc file by using Xpsdocument Close