With the current implementation, the Trigger Events are skippet on import.

From the PDF Specification: An annotation, page object, or interactive form field may include an entry named AA that specifies an additional-actions dictionary that extends the set of events that can trigger the execution of an action.

Implement importing and exporting the javascript actions associated with push button fields so that they can be executed when the exported document is opened with Adobe Acrobat. Javascript actions are also used by text fields for text validation (for instance for date input).

Implement page border property which could be applied over the whole document or over a specific page.

Introduce API for setting Image opacity.

The attached Workaround demonstrates how to change the opacity of the image before inserting it into the document.

Add support for documents containing RTL (right-to-left) text.

https://support.microsoft.com/en-us/office/display-or-hide-chart-gridlines-1f49f49c-a09f-4221-b2e5-269646f0deaa

Error bars in charts you create can help you see margins of error and standard deviations at a glance. They can be shown on all data points or data markers in a data series as a standard error amount, a percentage, or a standard deviation. You can set your own values to display the exact error amounts you want. 

https://support.microsoft.com/en-us/office/add-change-or-remove-error-bars-in-a-chart-e6d12c87-8533-4cd6-a3f5-864049a145f0 

Currently, the chart is generated considering the format applied to the cells. Thus, when the decimal part is clipped, duplicated values may occur and the developer doesn't have the option to update it:

This is the code:

            Workbook workbook = new Workbook();
            Worksheet worksheet = workbook.Worksheets.Add();

            List<string> categories = new List<string> { "New", "In Progress", "Ready for Test", "Done", "Declined" };
            worksheet.Cells[0, 0].SetValue("New");
            worksheet.Cells[0, 1].SetValue(1);
            worksheet.Cells[0, 2].SetValue(2.5);
            worksheet.Cells[1, 0].SetValue("In Progress");
            worksheet.Cells[1, 1].SetValue(2.8);
            worksheet.Cells[1, 2].SetValue(0);
            worksheet.Cells[2, 0].SetValue("Ready for Test");
            worksheet.Cells[2, 1].SetValue(2);
            worksheet.Cells[2, 2].SetValue(1);
            worksheet.Cells[3, 0].SetValue("Done");
            worksheet.Cells[3, 1].SetValue(1.4);
            worksheet.Cells[3, 2].SetValue(0);
            worksheet.Cells[4, 0].SetValue("Declined");
            worksheet.Cells[4, 1].SetValue(3);
            worksheet.Cells[4, 2].SetValue(0);

            

            FloatingChartShape chartShape = new FloatingChartShape(worksheet, new CellIndex(5, 5), new CellRange(0, 0, 4, 2),ChartType.Column)
            {
                Width = 400,
                Height = 250
            };

            worksheet.Charts.Add(chartShape);

            CellSelection cellSelection = worksheet.Cells[new CellIndex(0, 1), new CellIndex(4, 2)];
            CellValueFormat specialFormat = new CellValueFormat("0");
            cellSelection.SetFormat(specialFormat);

            string outputFilePath = "SampleFile.xlsx";

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

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

The requires options are setting the major/minor units for the axis:

At this point, the justify alignment is not supported. Provide the ability to export text with this setting.
This functionality is dependent on PdfProcessing: Provide API for setting the text alignment to Justify

Generate a document with the following approach: https://docs.telerik.com/devtools/document-processing/knowledge-base/populate-table-data-mail-merge

Before calling MailMerge, add two document variables with the editor: https://docs.telerik.com/devtools/document-processing/libraries/radwordsprocessing/concepts/fields/document-variables 

Typically, it is the text to be displayed for the annotation or, if the annotation does not display text, an alternate description of the annotation’s contents in human-readable form.

This item will be closed as its subject is too broad. Please refer to the information below for the individual markup annotations.

As of now, the currently supported markup annotations are:

Text
Line
Highlight
Underline
Squiggly
StrikeOut
Stamp

The unsupported annotations and their respective feedback items are:

FreeText
Square
Circle
Polygon
PolyLine
Caret
Ink
FileAttachment
Sound

PdfStreamWriter: "InvalidOperationException: 'isContentReleased'" is thrown when creating a multi-page document with an umlaut on the last page.

block.TextProperties.Font = FontsRepository.Courier;