It would be great if the SkiaImageExportSettings offer a DocumentUnhandledException event allowing the developer to handle specific errors when exporting to image formats.

This would be an essential improvement in the existing Exception handling mechanism and would enable exporting PDF documents to images even though some parts of the image may not be completely supported: https://docs.telerik.com/devtools/document-processing/libraries/radpdfprocessing/features/handling-document-exceptions 

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: 

Handle documents with mismatched font Subtype and FontFile type when exporting PDF to image with SkiaImageFormatProvider.

Add support for "AcroSendMail:SendMail" named action.

Such a document can be considered as invalid. However, it would be good to provide functionality to handle it.  

Part 3 of the standard, published on October 15, 2012, differs from PDF/A-2 in only one regard: it allows embedding of arbitrary file formats (such as XML, CSV, CAD, word-processing documents, spreadsheet documents, and others) into PDF/A conforming documents.

Purpose: Long-term archiving of electronic documents with full semantic structure.

• "A" for Archiving

• Level "1a" ensures:

  • Tagged PDF (with proper logical structure and reading order)

  • Unicode text for proper text extraction and searchability

  • Embedded fonts (for consistent rendering)

• Restrictions:

  • No audio/video

  • No encryption

  • No JavaScript

  • No external content (everything must be self-contained)

• Based on: PDF 1.4 (Acrobat 5)

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

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.

Introduce support for UnShrinking - Method 1.

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.

Export AdditionalActions of the page when merging pages with PdfStreamWriter.

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.

The hierarchical document structure is a means to describe the PDF document structure, which is currently not supported. See 10.6.1 Structure Hierarchy on 856 page of the PDF specification for details.
This document structure is an alternative to the standard PDF structure and most non-Adobe software does not support it.

The document might have been created with Adobe software like Adobe LiveCycle Designer. Very often the document contains some fallback text in the standard PDF structure like:
"Please wait... If this message is not eventually replaced by the proper contents of the document, your PDF viewer may not be able to display this type of document."
"The document you are trying to load requires Adobe Reader 8 or higher. You may not have the Adobe Reader installed or your viewing environment may not be properly configured to use Adobe Reader. For information on how to install Adobe Reader and configure your viewing environment please see  http://www.adobe.com/go/pdf_forms_configure."
"For the best experience, open this PDF portfolio in Acrobat X, Reader X, or later."

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'.'

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