Restrict the TableCellProperties API of a style according to specification.

When table with table border without color set is created (the color is null), and the document is exported to PDF, ArgumentNullException is thrown. 

Workaround: Explicitly set a color where the color is null.
private void PdfExport()
{
	var tables = this.document.EnumerateChildrenOfType<Table>();

	foreach (var table in tables)
	{
		TableBorders coloredClone = this.CopyTableBorders_SetColorWhenOmitted(table);
		table.Borders = coloredClone;
		
		using (Stream output = new FileStream(fileName, FileMode.OpenOrCreate))
		{
			provider.Export(this.document, output);
		}
	}
}

private TableBorders CopyTableBorders_SetColorWhenOmitted(Table table)
{
	var leftBorder = new Border(table.Borders.Left.Thickness,
				  table.Borders.Left.Style,
				  table.Borders.Left.Color ?? new ThemableColor(Colors.Transparent),
				  table.Borders.Left.Shadow,
				  table.Borders.Left.Frame,
				  table.Borders.Left.Spacing);

	var rightBorder = new Border(table.Borders.Right.Thickness,
				  table.Borders.Right.Style,
				  table.Borders.Right.Color ?? new ThemableColor(Colors.Transparent),
				  table.Borders.Right.Shadow,
				  table.Borders.Right.Frame,
				  table.Borders.Right.Spacing);

	var bottomBorder = new Border(table.Borders.Bottom.Thickness,
				table.Borders.Bottom.Style,
				table.Borders.Bottom.Color ?? new ThemableColor(Colors.Transparent),
				table.Borders.Bottom.Shadow,
				table.Borders.Bottom.Frame,
				table.Borders.Bottom.Spacing);

	var topBorder = new Border(table.Borders.Top.Thickness,
				table.Borders.Top.Style,
				table.Borders.Top.Color ?? new ThemableColor(Colors.Transparent),
				table.Borders.Top.Shadow,
				table.Borders.Top.Frame,
				table.Borders.Top.Spacing);

	var insideHorizontalBorder = new Border(table.Borders.InsideHorizontal.Thickness,
			 table.Borders.InsideHorizontal.Style,
			 table.Borders.InsideHorizontal.Color ?? new ThemableColor(Colors.Transparent),
			 table.Borders.InsideHorizontal.Shadow,
			 table.Borders.InsideHorizontal.Frame,
			 table.Borders.InsideHorizontal.Spacing);

	var insideVerticalBorder = new Border(table.Borders.InsideVertical.Thickness,
			table.Borders.InsideVertical.Style,
			table.Borders.InsideVertical.Color ?? new ThemableColor(Colors.Transparent),
			table.Borders.InsideVertical.Shadow,
			table.Borders.InsideVertical.Frame,
			table.Borders.InsideVertical.Spacing);

	var tableBorders = new TableBorders(leftBorder, topBorder, rightBorder, bottomBorder, insideHorizontalBorder, insideVerticalBorder);

	return tableBorders;
}

Center alignment is not respected for list numbering.

Expected:

Actual:

When a document with multiple headings ( Heading 1) are imported and then exported, their type from letters is changed to numbers, for example:

Original content: Part A, Part B, Part C

Exported content: Part 1, Part 2, Part 3

The generated document looks OK before printing:

However, hitting the print preview button in MS Words leads to missing text in the fields:

Add support for importing the text values of the input element. They could be imported as a simple text to preserve the content.

This is the code snippet that reproduces the error:

            RadFlowDocument flowDocument = new RadFlowDocument();
            RadFlowDocumentEditor editor = new RadFlowDocumentEditor(flowDocument);
            Bookmark bookmark = new Bookmark(flowDocument, "Name");
            editor.InsertInline(bookmark.BookmarkRangeStart);

            Table table = editor.InsertTable(1, 2);
            TableCell cell1 = table.Rows[0].Cells[0];
            Paragraph cell_paragraph1 = cell1.Blocks.AddParagraph();
            editor.MoveToParagraphStart(cell_paragraph1);
            editor.InsertText("cell content 01");

            TableCell cell2 = table.Rows[0].Cells[1];
            Paragraph cell_paragraph2 = cell2.Blocks.AddParagraph();
            editor.MoveToParagraphStart(cell_paragraph2);
            editor.InsertText("cell content 02");

            editor.MoveToTableEnd(table);
            editor.InsertInline(bookmark.BookmarkRangeEnd); 

            RadFlowDocument newFlowDocument = new RadFlowDocument();
            RadFlowDocumentEditor editor02 = new RadFlowDocumentEditor(newFlowDocument);
            editor.InsertDocument(flowDocument);

Workaround: Insert one bookmark before the table and another one after the table: 

            RadFlowDocument flowDocument = new RadFlowDocument();
            RadFlowDocumentEditor editor = new RadFlowDocumentEditor(flowDocument);
            //Bookmark bookmark = new Bookmark(flowDocument, "Name");
            //editor.InsertInline(bookmark.BookmarkRangeStart);

            editor.InsertBookmark("before");

            Table table = editor.InsertTable(1, 2);
            TableCell cell1 = table.Rows[0].Cells[0];
            Paragraph cell_paragraph1 = cell1.Blocks.AddParagraph();
            editor.MoveToParagraphStart(cell_paragraph1);
            editor.InsertText("cell content 01");

            TableCell cell2 = table.Rows[0].Cells[1];
            Paragraph cell_paragraph2 = cell2.Blocks.AddParagraph();
            editor.MoveToParagraphStart(cell_paragraph2);
            editor.InsertText("cell content 02");

            editor.MoveToTableEnd(table);

            editor.InsertBookmark("after");

            //editor.InsertInline(bookmark.BookmarkRangeEnd); 

            RadFlowDocument newFlowDocument = new RadFlowDocument();
            RadFlowDocumentEditor editor02 = new RadFlowDocumentEditor(newFlowDocument);
            editor.InsertDocument(flowDocument);