XlsFormatProvider: InvalidOperationException is thrown when importing a document with an unsupported BIFF record.

Workaround: Re-save the file with Excel before importing it.

The issue is reproducible with PDF form fields and setting Polish characters to the text fields: e.g. "ęóąśłżźćń" 

Edit mode in RadPdfViewer:

Exit edit mode:

Here is a sample code snippet for reproducing the case without UI:

            PdfFormatProvider provider = new PdfFormatProvider();
            RadFixedDocument document = provider.Import(File.ReadAllBytes("file.pdf"), TimeSpan.FromSeconds(10));

            foreach (RadFixedPage page in document.Pages)
            {
                foreach (Annotation annotation in page.Annotations)
                {
                    if (annotation.Type == AnnotationType.Widget)
                    {
                        Widget widget = (Widget)annotation;
                        var field = widget.Field as TextBoxField;
                        if (field != null) 
                        {
                            field.Value = "ęóąśłżźćń.";
                        }
                    }
                }
            }
            string outputFilePath = "result.pdf";
            File.Delete(outputFilePath);
            File.WriteAllBytes(outputFilePath, provider.Export(document, TimeSpan.FromSeconds(10)));
            Process.Start(new ProcessStartInfo() { FileName = outputFilePath, UseShellExecute = true });

After merging several PDF documents, some pages are blank indicating the following error:

Add support for strikethrough font effect for cell formatting. Currently this is not supported by the model and is omitted on import.

When using Telerik Document Processing (PdfProcessing) for embedding Factur-X invoices, the produced PDF document is Non‑compliant with PDF-AF / Factur‑X according to the following validator: 

https://www.superpdp.tech/outils/validateur-facture-electronique/ 

With the current implementation when exporting a Stitching function all the containing functions are exported as Sampled functions even if they originally have been imported as Exponential interpolation functions, which leads to an increase in the size of the document.

More information can be found in the PDF Specification.

This is preserved in the xml once saved from MS Excel:

Implement the Exponential Interpolation Function in PdfProcessing. Currently, NotSupportedFunctionTypeException is thrown with a message "Function type 2 is not supported."

The XlsxPartNames class expects a strict name for reading the comments parts:

public const string CommentsPartName = @"/xl/comments{0}.xml";

However, some third-party tools may change the name to GemComments.xml for example. 

MS Excel recognizes this naming for the comments part. It would be nice to provide such functionality in RadSpreadProcessing.

With the current implementation, the compression setting is omitted:

• streamWriter.Settings.StreamCompression

As a result of the below missing operator, some of the glyphs can't be extracted from the CFFFontTable and the characters are not displayed in the PdfViewer:

The end user result is missing letter from the PDF content.