Stretching the text is done by modifying the Scale Property of the Character Spacing properties. In the Office Open XML specification, it is represented by the <w:w w:val="300"/> tag. 

The commands that toggle different span styles (bold, italic, underline, strikethrough) stop working after using them several times on different ranges of cells. If a single cell is selected, the span could be properly changed.

The issue is reproducible with 2013 Q1 version and newer. It is not observed with version 2012 Q1.

Currently, there is an SDK example (https://github.com/telerik/xaml-sdk/tree/master/RichTextBox/WindowsMetafileFormatImageDecoder) showing how to implement a custom decoder that can import WMF and EMF images. We could integrate this decoder in the source code and enable the users to import their documents that contain such type of images out-of-the-box. 

Available in R1 2017 Official Release Version.

When a custom style is applied to a table and the document is exported to DOCX or RTF format, after importing and deleting the custom style, some properties like font size and foreground are preserved.

After inserting page break or section break the visual position of the caret is wrong. It should be at the beginning of the paragraph instead of beginning of the page. It's observed for all type of breaks except a line break. 

Section break formatting symbol is not positioned as in MS Word. 
For example, when section break is inserted in an empty document and the cursor is placed before the break, when Enter is pressed, the section break formatting symbol is moved to the next line. 
In MS Word, the section break is preserved on the same line with the paragraph symbol.

When a document has some section properties like orientation or page size and the document is printed with virtual printer, the generated PDF does not preserve the section properties. 

For example, if the document has Landscape orientation set, in the generated PDF file, the page with Landscape orientation is visualized with Portrait orientation and the text is drawn vertically.
If the document has some page size set, for example A5, in the generated PDF file, the page with size A5 is visualized as page with A4 page size.

Importing HTML document with white spaces and new lines separating the HTML elements will lead to additional intervals between words.

The width of the table cell is calculated wrongly when it is set in the CSS style and through attribute: <td style="WIDTH: 75%" width=450>First cell</td>. The Unit isn't reset while reading the attribute value as its unit is missing and it is interpreted as % because the previous value is in percent.

Line break has a specific property which should be taken into account only when there is a floating object which interrupts the line, e.g.:

<w:br w:type="textWrapping" w:clear="all" /> 

Adding a custom list could be done by using the AddCustomListStyle method of RadDocument. However, this operation will not be included in the Undo stack.

Deleting the full chain of relationships between a list style and a document list is not possible.

When editing header/footer in MS Word, the paragraph which is inserted there has defined tab stops. In RadRichTextBox there isn't and thus, when the tab is pressed, a default tab stop is inserted.

This functionality is not supported out-of-the-box. However, it could be implemented by the users as demonstrated in the Custom Code Formatting Language SDK example (https://github.com/telerik/xaml-sdk/tree/master/RichTextBox/CustomCodeFormattingLanguage).

Words containing apostrophes are not recognized by the spell checker. Examples: 
- Some contracted forms , for example "they've"
- A lot of common French words, e.g. "Aujourd’hui", "qu’une", "n'est"

The issue could be observed for the single straight (') as well as for the smart (’) quote.

Workaround:
Add the all word parts to the dictionary, for example, to recognize "they've", both "they" and "ve" should be added to the dictionary.

Fix available in LIB Version 2017.3.1009.

Importing HTML with "a:link" CSS style will be applied to the text in a bookmark. Here is example of such HTML:

<html>
  <head>
    <style type="text/css">
      a:link {
        text-decoration: underline;
      }
    </style>
  </head>
  <body>
    <a name="anchor">Anchor element</a>
  </body>
</html>

A possible workaround is to select the content between the bookmarks and apply different underline decoration. Here is example of how this could be done:

List<BookmarkRangeStart> bookmarks = document.EnumerateChildrenOfType<BookmarkRangeStart>().ToList();
foreach (var rangeStart in bookmarks)
{
    document.Selection.Clear();

    var start = new DocumentPosition(document);
    start.MoveToEndOfDocumentElement(rangeStart);

    var end = new DocumentPosition(document);
    end.MoveToEndOfDocumentElement(rangeStart.End);

    document.Selection.AddSelectionStart(start);
    document.Selection.AddSelectionEnd(end);

    RadDocumentEditor editor = new RadDocumentEditor(document);
    editor.ChangeUnderlineDecoration(UI.TextDecorations.DecorationProviders.UnderlineTypes.None);
}

document.Selection.Clear();

While typing in a document containing a table with nested table, and the table is moved to the next page because of the flow of the text, NullReferenceException is thrown. 

When such document is loaded in RadRichTextBox a NullReferenceException could be thrown depending of the exact document or the application will hangs (goes to infinite cycle during the document layout).

Available fix in LIB version 2017.1.410.

Scroll to the necessary value the vertical offset of the RadRichTextBox if header/footer is not in the viewport, but the editor goes into it.

Workaround: In the current implementation this could probably be achieved by using the ScrollToVerticalOffset method, but the calculations which should be done for the offset value might be not so straight-forward and easy to make. Here is a sample example of this:

this.radRichTextBox.ActiveDocumentEditorChanged += (s, e) =>
{
    if (e.DocumentEditorType == Telerik.Windows.Documents.UI.DocumentEditorType.Footer)
    {
        Section section = this.radRichTextBox.Document.CaretPosition.GetCurrentSectionBox().AssociatedSection;

        double offset = this.radRichTextBox.VerticalOffset + (section.PageSize.Height - section.ActualPageMargin.Bottom) * this.radRichTextBox.ScaleFactor.Height;
        this.radRichTextBox.ScrollToVerticalOffset(offset);
    }
};

As a user, I'd like to have a way to determine what document elements or layout boxes are in the view port. I may need them in order to:

- Modify something else in the UI depending on them. For example, if a hyperlink or bookmark is scrolled in the viewport, enable buttons outside RichTextBox that execute specific actions.
- Implement formatting changes to the visible elements only in scenarios like a code editor.

Right now, the only way to obtain the visible boxes is to implement a UI layer, however, layers are intended for scenarios in which you'd like to modify the presentation of the control's content and may not be a good idea to utilize them for formatting changes or other actions.

In MS Word, images can have strikethrough formatting. In RadDocument's model, this is property of Spans only.

For example, if the document has "Times New Roman" as a default font family, the "TableNormal" style doesn't have set that property and there is a Table element in the header - the value is not properly obtained ("Verdana" is applied, which is the default value for that Span property).
The problem is observed for all default span style properties.

Workaround: Change the table style by setting the necessary properties from the default style. For example for the font family:

object documentFontFamilyPropertyValue = this.radRichTextBox.Document.Style.GetPropertyValue(Span.FontFamilyProperty);
foreach (StyleDefinition tableStyle in this.radRichTextBox.Document.StyleRepository.Where(s => s.Type == StyleType.Table && s.BasedOn == null))
{
    StylePropertyBase styleProperty = tableStyle.GetProperty(Span.FontFamilyProperty);
    if (styleProperty.ValueSource == RadValueSource.Default)
    {
        tableStyle.SetPropertyValue(Span.FontFamilyProperty, documentFontFamilyPropertyValue);
    }
}