Inserting a single-cell table with top border is a common workaround for the missing 'horizontal line' functionality. 

Exporting such table to PDF causes wrong result if the intercepting vertical borders are of type None and have smaller thickness.

Attached image outlines the issue.

Workaround: Set the same thickness to the noBorder and to the visible border:
var t = new Telerik.Windows.Documents.Model.Table(1, 1);\
var noBorder = new Telerik.Windows.Documents.Model.Border(3, BorderStyle.None, Colors.Black);
t.Borders = new TableBorders(noBorder, new Telerik.Windows.Documents.Model.Border(3, BorderStyle.Single, Colors.Black), noBorder, noBorder);


Steps to reproduce:
1. Insert table with the following code:

            var t = new Telerik.Windows.Documents.Model.Table(1, 1);
            var noBorder = new Telerik.Windows.Documents.Model.Border(BorderStyle.None);
            t.Borders = new TableBorders(noBorder, new Telerik.Windows.Documents.Model.Border(3, BorderStyle.Single, Colors.Black), noBorder, noBorder);

            this.radRichTextBox.InsertTable(t);
2. Export to PDF

When Insert date command through "Date & Time" button is executed for the first time, the date is added to the document as expected. However, if the date is inserted once again, then the date is inserted twice. If date is inserted for the third time in the document, then it will be inserted three times and so on.

Pressing Enter in the first empty cell in the second table of two adjoined tables adds the paragraph between the tables. Instead, the paragraph should be added in the cell.

Steps to reproduce:
- Add two tables.
- Remove the paragraph between them (using the Delete key).
- Add paragraph in the first cell of the second table.
Expected: The paragraph is added in the cell.
Actual: The tables are separated by paragraph.

When RTF documents are imported simultaneously in different threads, sometimes ArgumentException with message "An item with the same key has already been added" is thrown with the following call stack:

at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)
   at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value)
   at Telerik.Windows.Documents.FormatProviders.ReplaceStyleNameHandler.Add(String displayName, String name)
   at Telerik.Windows.Documents.FormatProviders.ReplaceStyleNameHandler.InitializeStyleDisplayNameToStyleNameDictionary()
   at Telerik.Windows.Documents.FormatProviders.ReplaceStyleNameHandler.get_StyleDisplayNameToStyleName()
   at Telerik.Windows.Documents.FormatProviders.ReplaceStyleNameHandler.TryGetStyleNamesByStyleName(String displayName, RadDocumentDefaultStyleInfo& defaultStyleInfo)
   at Telerik.Windows.Documents.FormatProviders.ReplaceStyleNameHandler.Replace(ReplaceStyleNameContext context)
   at Telerik.Windows.Documents.FormatProviders.Rtf.Import.RtfStyleImporter.DoVisitText(RtfText text)
   at Telerik.Windows.Documents.FormatProviders.Rtf.Import.RtfElementIteratorBase.VisitElement(RtfElement element, Boolean recursive)
   at Telerik.Windows.Documents.FormatProviders.Rtf.Import.RtfElementIteratorBase.VisitGroupChildren(RtfGroup group, Boolean recursive)
   at Telerik.Windows.Documents.FormatProviders.Rtf.Import.RtfStyleImporter.ImportStyleGroup(RtfGroup group)
   at Telerik.Windows.Documents.FormatProviders.Rtf.Import.RtfStylesTable.FillStyle(RtfGroup group, StyleType type, Boolean isDefault)
   at Telerik.Windows.Documents.FormatProviders.Rtf.Import.RtfStylesTable.DoVisitGroup(RtfGroup group)
   at Telerik.Windows.Documents.FormatProviders.Rtf.Import.RtfElementIteratorBase.VisitElement(RtfElement element, Boolean recursive)
   at Telerik.Windows.Documents.FormatProviders.Rtf.Import.RtfElementIteratorBase.VisitGroupChildren(RtfGroup group, Boolean recursive)
   at Telerik.Windows.Documents.FormatProviders.Rtf.Import.RtfStylesTable.ReadTable(RtfGroup group, RtfImportContext context)
   at Telerik.Windows.Documents.FormatProviders.Rtf.Import.RtfHandlers.RtfGroupHandlers.StylesTableHandler(RtfGroup group, RtfImportContext context)
   at Telerik.Windows.Documents.FormatProviders.Rtf.Import.RtfDocumentImporter.DoVisitGroup(RtfGroup group)
   at Telerik.Windows.Documents.FormatProviders.Rtf.Import.RtfElementIteratorBase.VisitElement(RtfElement element, Boolean recursive)
   at Telerik.Windows.Documents.FormatProviders.Rtf.Import.RtfElementIteratorBase.VisitGroupChildren(RtfGroup group, Boolean recursive)
   at Telerik.Windows.Documents.FormatProviders.Rtf.Import.RtfDocumentImporter.ImportRoot(RtfGroup rtfGroup)
   at Telerik.Windows.Documents.FormatProviders.Rtf.Import.RtfDocumentImporter.Import(Stream input, RtfImportSettings settings)
   at Telerik.Windows.Documents.FormatProviders.Rtf.RtfFormatProvider.Import(Stream input)
   at Telerik.Windows.Documents.FormatProviders.Rtf.RtfFormatProvider.Import(String input)

Fix available in LIB Version 2018.3.924.

The flow direction of a paragraph is automatically changed to right-to-left if all spans in the paragraph are in the right-to-left mode when importing from DOCX format.

Open a docx file in richtextbox, if numpages in headers do any subtraction, it can not display correctly. see the attached pictures for how to display in richtextbox and microsoft word 2016.

This feedback item is duplicated. Here is the link to the original bug report: https://feedback.telerik.com/Project/143/Feedback/Details/145511-richtextbox-incorrect-layout-and-export-of-bi-directional-mixed-text-containin

Hyperlink without any navigational information will crash the application with NullReferenceException when showing it.

Bookmarks are not imported and missing from a specific document scenario.

Workaround: Import and then export the document using the WordsProcessing library and then open it with the editor.

please add shapes support for radrichtextbox. else support another textbox

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);
    }
};

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.

This element specifies the presence of a symbol character at the current location in the run’s content. It is similar to the sym element and is used to add emojis to the document content. The symEx element is not defined in the Office Open XML specification but it is part of the extensions of MS Word to the Office Open XML.

Currently one can insert emojis by pressing "Ctrl + .". However, the emojis are inserted in black and white. 

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();

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.

Add support for lower-alpha and upper-alpha.