Add support for Paragraph and Page borders.

Note: Typing "---" in MS Word and pressing Enter inserts bottom paragraph border with special size (sz="6" in the docx format).

Workaround for inserting visually similar element:

Add a horizontal line using a table with a single border. Here is some code demonstrating how to do this:
----------------------------------------------------------
var document = new RadDocument();
var editor = new RadDocumentEditor(document);

Table table = new Table();
var topBorder = new Telerik.Windows.Documents.Model.Border(1, BorderStyle.Single, Colors.Red);
var borders = new TableBorders(table.Borders.Left, topBorder, table.Borders.Right, table.Borders.Bottom);
table.Borders = borders;

var row = new TableRow();
var dummyCell = new TableCell();
var dummyParagraph = new Paragraph();
dummyParagraph.FontSize = 0;
dummyParagraph.LineSpacing = 0;
dummyParagraph.SpacingAfter = 0;
dummyParagraph.SpacingBefore = 0;
dummyCell.Blocks.Add(dummyParagraph);
row.Cells.Add(dummyCell);
table.Rows.Add(row);

editor.InsertTable(table, shouldInsertParagraphBeforeTable: true);            
this.rtb.Document = document;
----------------------------------------------------

In MS Word, there is special command in Home -> Paragraph -> Borders dropdown -> Horizontal Line, which inserts special drawing similar to 3D horizontal line in a paragraph. Such line should be exported to <hr> tag during HTML export, and respectively <hr> tag should be imported as Horizontal Line.

Note: the representation of the horizontal line in the docx document is as follows: 

        <w:pict>
          <v:rect id="_x0000_i1027" style="width:0;height:1.5pt" o:hralign="center" o:hrstd="t" o:hr="t" fillcolor="#a0a0a0" stroked="f"/>
        </w:pict>

Workaround: 
Currently, you can add a horizontal line using a table with a single border. Here is some code demonstrating how to do this:

----------------------------------------------------------

var document = new RadDocument();
var editor = new RadDocumentEditor(document);

Table table = new Table();
var topBorder = new Telerik.Windows.Documents.Model.Border(1, BorderStyle.Single, Colors.Red);
var borders = new TableBorders(table.Borders.Left, topBorder, table.Borders.Right, table.Borders.Bottom);
table.Borders = borders;

var row = new TableRow();
var dummyCell = new TableCell();
var dummyParagraph = new Paragraph();
dummyParagraph.FontSize = 0;
dummyParagraph.LineSpacing = 0;
dummyParagraph.SpacingAfter = 0;
dummyParagraph.SpacingBefore = 0;
dummyCell.Blocks.Add(dummyParagraph);
row.Cells.Add(dummyCell);
table.Rows.Add(row);
			
editor.InsertTable(table, shouldInsertParagraphBeforeTable: true);            
this.radRichTextBox.Document = document;

----------------------------------------------------

There is already Author property but it is not filled automatically. It should be filled using the RequestCurrentUserInfo event of the RadDocument, which is currently only used for track changes revisions. 

When importing image with invalid ur/base64 encoded data the document won't be opened correctly and an exception will be thrown. Load default image instead of throwing exception and failing to open the document.

Citations should be exported  as blockquotes in HTML

RichTextBox: Add Word like selection where the entire word is selected when moving forward. When moving backward only the characters are deselected. 

In MergeFields the general switch may be used to format the Result Text. The text may appear in lowercase, uppercase, title case and so on.

The MS Word has a context menu option Remove Content Control which is missing in the RadRichTextBox UI.

The scenario:

We have a document with text inside and we are executing the following steps:

1. Mouse left button down.
2. Select part of the text.
3. Replace the selection with new text programmatically (the text should be with a different length).
4. Release the left button.

Observed: Before releasing the mouse button the cursor position is correct but after releasing it the cursor position is changed to the initial selection end.

Add support for comparing documents.

When users select content in RadRichTextBox, the selection is automatically extended to include the whole annotation range and they cannot select only a part of it. Allow users to disable that extension.

The highlight text button in the ribbon has an invalid icon 

Provide an option for having a single page even if there is space for more. On a large widescreen monitor, DocumentPrintLayoutPresenter/PagesLayoutManager positions pages side-by-side rather than in a single column.

Internal exception of type NullReferenceException is thrown when the field has an empty code fragment.

Merge undo commands when typing consecutive text. In Word when typing continuous text (without changing the caret position) it is added as only one undo step. In RichTextBox every keystroke (or multiple keystrokes with less than 15 milliseconds in delay) is added as separate undo steps.

Add support for line numbering in paged layout mode, similar to MS Word.

The line numbers are currently skipped on export to PDF.

In my usage scenario,  I want to allow the users to do some specific actions like changing the font or inserting a table row in those restricted areas.

My current implementation is to modify the source code of RadRichTextBox, expose RespectDocumentProtection and RespectNonDeletableRanges, and temporarily set these properties to false before performing modifications in those restricted areas.

Currently, the properties are available in RadDocumentEditor only.

No visual cue when image deleted or inserted when "Track changes" is activated. 

When inserting an image with the Track Changes option toggled, the image should be underlined with red and it isn't. When deleting an image with Track Changes on, it is also not crossed with red. In both cases, the only mark that a change was made is the vertical line on the left.

Implement the export of notes (footnote, endnote) in the PdfFormatProvider of the RadRichTextBox.