Workbook wb = new Workbook();
            Worksheet worksheet = wb.Worksheets.Add(); 
            PatternFill fill = new PatternFill(PatternType.DiagonalStripe, Colors.Red, Colors.Transparent);
            worksheet.Cells[0, 0].SetFill(fill);

            string outputFilePath = "Sample.pdf";
            File.Delete(outputFilePath);
            Telerik.Windows.Documents.Spreadsheet.FormatProviders.Pdf.PdfFormatProvider pdfFormatProvider =
                new Telerik.Windows.Documents.Spreadsheet.FormatProviders.Pdf.PdfFormatProvider(); 
          
            //export to file
            using (Stream output = File.OpenWrite(outputFilePath))
            {
                pdfFormatProvider.Export(wb, output, TimeSpan.FromSeconds(10));
            }

            Process.Start(new ProcessStartInfo() { FileName = outputFilePath, UseShellExecute = true });

WorksheetPageSetup pageSetup = workbook.ActiveWorksheet.WorksheetPageSetup;
pageSetup.PrintTitles.RepeatedRows = null;
pageSetup.PrintTitles.RepeatedColumns = null;

   at System.ThrowHelper.ThrowArgumentNullException(ExceptionArgument argument)
   at System.Collections.Generic.Dictionary`2.FindValue(TKey key)
   at System.Collections.Generic.Dictionary`2.ContainsKey(TKey key)
   at Telerik.Windows.Documents.Spreadsheet.FormatProviders.OpenXml.Xlsx.Model.Elements.Worksheets.ConditionalFormattingRuleElementX14.OnAfterRead(IXlsxWorksheetImportContext context) in C:\Work\document-processing\Documents\Spreadsheet\FormatProviders\OpenXml\Xlsx\Model\Elements\Worksheets\ConditionalFormatting\x14\ConditionalFormattingRuleElementX14.cs:line 62

            string inputFileName = "input.xlsx";
            if (!File.Exists(inputFileName))
            {
                throw new FileNotFoundException(String.Format("File {0} was not found!", inputFileName));
            }

            Telerik.Windows.Documents.Spreadsheet.Model.Workbook workbook;
            IWorkbookFormatProvider formatProvider = new Telerik.Windows.Documents.Spreadsheet.FormatProviders.OpenXml.Xlsx.XlsxFormatProvider();

            using (Stream input = new FileStream(inputFileName, FileMode.Open))
            { 
                workbook = formatProvider.Import(input, TimeSpan.MaxValue);
            }
            string outputFilePath = "output.xlsx";

            using (Stream output = new FileStream(outputFilePath, FileMode.Create))
            {
                formatProvider.Export(workbook, output, TimeSpan.MaxValue);
            }
            Process.Start(new ProcessStartInfo() { FileName = outputFilePath, UseShellExecute = true });