When the document contains an encrypted Hex string in Bookmark titles the strings are not decrypted and they are wrongly displayed.

The observed result using the WPF PdfViewer:

I have the following form:

From the screen shot above you can see that the line above 75 is perfectly ok i.e. it doesn't go and intersect with the lines of the 72

but when i perform the following code

            var InputFileWithInteractiveForms = "C:\\Users\\Abhishek.Shrestha\\Downloads\\Template\\form-ub04.pdf";
            var finaldPDFName = "C:\\Users\\Abhishek.Shrestha\\Downloads\\TestABCPDF\\output2322.pdf";
            List<byte[]> filledupForms = new List<byte[]>();
            PdfFormatProvider provider = new PdfFormatProvider();
                
                RadFixedDocument document = provider.Import(File.ReadAllBytes(InputFileWithInteractiveForms));

                var formfields = document.AcroForm.FormFields;

                var formFieldsCopy = new List<FormField>(document.AcroForm.FormFields);

                // Iterate over the copied form fields and replace the dot character in their names for solving merging issue
                foreach (var field in formFieldsCopy)
                {
                    field.Name = field.Name.Replace(".", "");
                }
                
               //added this as the values were being hidden by editable fields
                document.AcroForm.ViewersShouldRecalculateWidgetAppearances = true;

                filledupForms.Add(provider.Export(document));
                File.WriteAllBytes(finaldPDFName, provider.Export(document));

I get the following output:


               

Support for exporting WEBP images should be implemented.

Importing a document containing an EI keyword not followed by space or return leads to an endless loop and the document is not imported successfully.

Expected:

Actual:

After the import-export of a specific document, the paths are thinner and the corners of the path figure are not rounded:

 

 

Encryption Algorithm 4 is implemented for R1 2018 official release. This includes all encryptions except AES 256 which is related to Encryption Algorithm 5. For AES 256 you may vote and follow this feedback item:
https://feedback.telerik.com/Project/184/Feedback/Details/240154-pdfprocessing-support-encryption-algorithm-5-with-aes-256

This would ensure preserving the existing PDF file pages and document properties untouched and additionally would allow making a few modifications to the file. By appending bytes to existing PDF file one may achieve:

 - Modifying specific pages content and properties.
 - Adding new pages to pages collection.
 - Modify some document properties (such as Bookmarks).
 - Edit interactive forms field values.
 - Add digital signatures to existing documents.

This type of destinations is not supported and leads to InvalidCastException when importing such elements.

Currently, there is no way to know when a new page is created when content "overflows" to the next page 

This event may be needed in order to generate the header and footer based on the currently generated content. In simple header/footer scenarios, however, this event may not be needed and the headers and footers may be drawn after all pages are generated as described in the comments below.

InvalidOperationException is thrown when exporting font that is available but not used.

The stack trace is as follows:
   at System.Linq.Enumerable.Max(IEnumerable`1 source)
   at Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Model.Elements.Fonts.Cid.CidSet.CopyPropertiesFrom(IPdfExportContext context, FontBase font)
   at Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Model.Elements.Fonts.CidFontDescriptor.CalculateCidSet(IPdfExportContext context, CidFontBase font)
   at Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Model.Elements.Fonts.CidFontDescriptor.<>c__DisplayClass34.<CopyPropertiesFrom>b__30()
   at Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Utilities.PdfObjectsExtensions.ToPrimitive[P,T](PdfProperty`1 pdfProperty, Func`2 convertToPrimitive, Func`1 getDefaultValue)
   at Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Model.Elements.Fonts.CidFontDescriptor.CopyPropertiesFrom(IPdfExportContext context, FontBase font)
   at Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Model.Elements.Fonts.CidFontObject.CopyPropertiesFromOverride(IPdfExportContext context, FontBase font)
   at Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Model.Elements.Fonts.CidFontObject.CopyPropertiesFrom(IPdfExportContext context, FontBase font)
   at Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Model.Elements.Fonts.Type0FontObject.CopyPropertiesFromOverride(IPdfExportContext context, FontBase font)
   at Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Export.PdfExporter.WriteFontsFromContext(PdfWriter writer, IPdfExportContext context)
   at Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Export.PdfExporter.Export(IRadFixedDocumentExportContext context, Stream output)
   at Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.PdfFormatProvider.ExportOverride(RadFixedDocument document, Stream output)
   at Telerik.Windows.Documents.Common.FormatProviders.FormatProviderBase`1.Export(T document, Stream output)

The exception is thrown with the message "Password is not correct" even when the user password is correct. This issue occurs for specific encryption algorithm parameters only.

This includes loading form fields data from FDF file and saving the form fields data to FDF file.

This exception seems to be related to AES algorithm PaddingMode property. 

While signing a document in Adobe Reader, the users can lock the document fields from editing. Expose a similar functionality.

The feature is described by the FieldMDP transform method, described on page 736 from the Pdf Reference 1.7

The case is invalid according to the specification but all readers manage to open the document and allow editing its fields. The document can be also opened in RadPdfViewer but without the fields and the widgets.

RadPdfProcessing cannot find startxref keyword at the end of a document if the document contains many zero bytes at its end. NotSupportedException is thrown with "Startxref keyword cannot be found" message. 
Workaround: Trim the ending zero bytes before loading the document to PdfProcessing. Example showing this approach can be found in the following KB article:
http://www.telerik.com/support/kb/winforms/details/notsupportedexception-startxref-keyword-cannot-be-found-when-loading-pdf-file-in-radpdfviewer-for-winforms

Documents can be signed using the end certificate of a certificate chain, instead of the whole chain. This improves the performance of the signing.

When merging files the documents might have the same fonts embedded. Then the PdfProcessing should use only one of the fonts and skip embedding the second font in the resulting document.