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

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

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

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

The current formula: 
<c r="A1" s="1">
<f>[1]BILANS_JI!$C$2</f>
<v>22611518.026189998</v>
</c>

• Simple direct reference to a single external cell [1]BILANS_JI!$C$2
• No function, just a linked cell

The expected value to be returned is 22611518.

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 });

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/