A shading dictionary specifies details of a particular gradient fill, including the
type of shading to be used, the geometry of the area to be shaded, and the geometry of the gradient fill. Various shading types are available, depending on the value of the dictionary’s ShadingType entry:

• Coons patch meshes (type 6) construct a shading from one or more color
  patches, each bounded by four cubic Bézier curves.

When importing a document with a missing "endobj" operator, an exception is thrown: InvalidCastException: 'Unable to cast object of type 'Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Model.Types.PdfInt' to type 'Telerik.Windows.Documents.Fixed.FormatProviders.Pdf.Model.Types.IndirectObject'.'

Currently, the SkiaImageFormatProvider considers the RadFixedPage.Size when creating the image. If the RadFixedPage.CropBox is specified, the developer can control what rectangle of the page to be displayed/printed. However, it is not considered when exporting to an image. Improving the SkiaImageFormatProvider to respect the CropBox as well will give the opportunity to crop just a certain region of the PDF page and save it as an image.

Handle the import of documents with Associated Files (/AF) elements whose content is set to null.

Handle the import of documents with null elements in the Associated Files (/AF) collection.

Implement functionality to support scenario when a document which already has a signature to be signed again or add two or more signatures.

This type of action is currently not supported and a NotSupportedActionException is thrown when accessing such an object.

These exceptions can be handled using the Handling Exceptions mechanism.

Add support for GoToR action

Note: related item: PdfProcessing: Introduce functionality to preserve GoToR actions during import/export

When exporting the PDF content to plain text, the form fields and their values are not extracted. It would be nice to have an option to include the content in the form fields as well.

Introduce Sanitize Document functionality.

https://experienceleague.adobe.com/en/docs/document-cloud-learn/acrobat-learning/advanced-tasks/redact
https://helpx.adobe.com/acrobat/using/removing-sensitive-content-pdfs.html

Export AdditionalActions of the page when merging pages with PdfStreamWriter.

In version 1 there are three profiles that have different levels of detail in their structure: Basic (B), Comfort (C) and Extended (X): https://mind-forms.de/e-rechnung/welches-zugferd-profil-kann-ich-verwenden/ 

For instance, we may implement WritePageAsync method in addition to the existing WritePage method. This is a similar scenario as in System.IO.StreamWriter class which has WriteLine and WriteLineAsync methods.

The PDF/A-1 standard uses the PDF Reference 1.4 and specifies two levels of compliance:

- PDF/A-1b - Its goal is to ensure reliable reproduction of the visual appearance of the document.

- PDF/A-1a - Its objective is to ensure that documents content can be searched and re-purposed. This compliance level has some additional requirements:

• Document structure must be included.
• Tagged PDF.
• Unicode character maps
• Language specification.

Since the PdfProcessing and its PdfFormatProvider is compliant with the PDF Reference 1.7. , the produced documents are created with this version as well: 

Handwritten Signature is a type of biometric signature that relies on capturing unique biometric data from a person's handwritten signature.

Introduce support for UnShrinking - Method 1.

This property should work similar to PreferredWidth cell property but in vertical direction.

Implement support for adding barcodes to a PDF document.

Optical character recognition or optical character reader (OCR) is the electronic or mechanical conversion of images of typed, handwritten, or printed text into a machine-encoded text from a scanned document.

Add support for Named Actions.