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;
}

When importing a document containing an invalid PDF object dictionary key an exception is thrown.

When importing a document with button field with missing type, an error occurs.

51 0 obj
<< /Kids [ 70 0 R 71 0 R 72 0 R 73 0 R 74 0 R 75 0 R 76 0 R 77 0 R 78 0 R 79 0 R 80 0 R 81 0 R 82 0 R 83 0 R 84 0 R 85 0 R 86 0 R 87 0 R 88 0 R 89 0 R 90 0 R 91 0 R 92 0 R 93 0 R 94 0 R 95 0 R 96 0 R 97 0 R 98 0 R 99 0 R 100 0 R 101 0 R 102 0 R 103 0 R 104 0 R 105 0 R 106 0 R 107 0 R 108 0 R 109 0 R 110 0 R 111 0 R 112 0 R 113 0 R 114 0 R 115 0 R 116 0 R 14 0 R ] /T (Button 70) >>
endobj

Workaround: Handle the exception: https://docs.telerik.com/devtools/document-processing/libraries/radpdfprocessing/features/handling-document-exceptions 

Add support for array formulas (CellFormulaType "array"). These formulas can accept as parameters and return results containing whole arrays (one- or two- dimensional) of data. In MS Excel, such formulas are inserted with CTRL + SHIFT + Enter, and visualized enclosed with curly brackets ('{' and '}'). 

Text frames are paragraphs of text in a document which are positioned in a separate region or frame in the document and can be positioned with a specific size and position relative to non-frame paragraphs in the current document. More information about it is available in section 22.9.2.18 ST_XAlign (Horizontal Alignment Location) of Open Office XML.