WPF DocumentViewer Find-function and FixedPage documents

.Net contains a nice control called DocumentViewer. it also offers a subcontrol for finding text in the loaded document (that's at least what it is supposed to do).

When inserting FixedPage's objects as document source for the DocumentViewer, the find-functionality just does not find anything. Not even single letters. I haven't tried FlowDocument's yet, as the documentation for DocumentViewer is not that useful and the resources on the net are not actually existing, I now want to ask the stackoverflow community:

What does it need to get the Find-Function of the WPF DocumentViewer working with FixedPage documents?

[btw, I don't use custom ControlTemplates for DocumentViewer]

I had this same problem with FixedDocuments. If you convert your FixedDocument to an XPS document then it works fine.

Example of creating an XPS Document in memory from a FixedDocument then displaying in a DocumentViewer.

// Add to xaml: <DocumentViewer x:Name="documentViewer" />
// Add project references to "ReachFramework" and "System.Printing"
using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.IO;
using System.IO.Packaging;
using System.Windows.Xps.Packaging;

namespace WpfApplication1
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            // Set up demo FixedDocument containing text to be searched
            var fixedDocument = new FixedDocument();
            var pageContent = new PageContent();
            var fixedPage = new FixedPage();
            fixedPage.Children.Add(new TextBlock() { Text = "Demo document text." });
            pageContent.Child = fixedPage;
            fixedDocument.Pages.Add(pageContent);

            // Set up fresh XpsDocument
            var stream = new MemoryStream();
            var uri = new Uri("pack://document.xps");
            var package = Package.Open(stream, FileMode.Create, FileAccess.ReadWrite);
            PackageStore.AddPackage(uri, package);
            var xpsDoc = new XpsDocument(package, CompressionOption.NotCompressed, uri.AbsoluteUri);

            // Write FixedDocument to the XpsDocument
            var docWriter = XpsDocument.CreateXpsDocumentWriter(xpsDoc);
            docWriter.Write(fixedDocument);

            // Display XpsDocument in DocumentViewer
            documentViewer.Document = xpsDoc.GetFixedDocumentSequence();
        }
    }
}