https://loc.gov/preservation/digital/formats/fdd/fdd000532.shtml

PDF/A‑4f is a version of PDF/A designed for archival storage that:

• Ensures long‑term visual and structural preservation
• Is based on modern PDF 2.0
• Allows embedded files (attachments) that are also archival‑compliant 

NetStandard: Missing content due to empty glyph outlines in embedded TrueType font subsets.

Workaround 1

Fully embed the fonts in the result PDF document:

PdfFormatProvider pdfFormatProvider = new PdfFormatProvider();
pdfFormatProvider.ExportSettings.FontEmbeddingType = FontEmbeddingType.Full;

Workaround 2

Switch to a .NET Framework project environment and use the .NET Framework PdfProcessing packages.

Here is a sample structure of the signature: 

/Type /Sig
/SubFilter /adbe.x509.rsa_sha1
/Filter /Adobe.PPKMS

InvalidOperationException is thrown when exporting a PDF document with a set compliance that processes Type3 font glyphs.

Workaround: Before export, set compliance to None.

var provider = new PdfFormatProvider();
provider.ExportSettings.ComplianceLevel = PdfComplianceLevel.None;

From R1 2017 all annotations (including sound and video) are supported for import-export scenarios by using PdfStreamWriter class. 

These feedback item will be opened as we may add API for generating and inserting new sound annotations from scratch in the file.

When a source RadFixedDocument is merged to a target RadFixedDocument, the content of the source document is cleared.

WinAnsiEncoding it is imported as StandardEncoding since WinAnsiEncoding is still not implemented in RadPdfProcessing. 

 This is content stream operator that is used to close, fill and then stroke a PDF path geometry.

Available in R3 2018 SP1 release.

When images are added to the document with non-default quality (PdfExportSettings.ImageQuality different that ImageQuality.High) , they are re-encoded, which uses a lot of memory and may cause OutOfMemoryException for large images.
Workaround (works when inserting big JPEG images): In this case ImageQuality.High may be used and RadPdfProcessing will decode only the image headers to insert the image into the PDF file. As image pixels are not decoded with ImageQuality.High, there will be no OutOfMemoryException.

This would allow creating documents with preferences such us HideToolbar, HideMenubar, FitWindow, PrintScaling and all other viewer preferences specified in PDF format specification.

OutOfMemoryException is thrown when generating PDF with many pages each of which contains images, as all of the document model data is in-memory.

The issue is fixed with the new PdfStreamWriter API. As an example, you may see the attached demo to the following feedback item:
https://feedback.telerik.com/Project/184/Feedback/Details/213503-pdfprocessing-optimize-pdfstreamwriter-cache-in-order-to-reduce-memory-when-writ

Available in LIB version: 2017.1.320