PdfStreamWriter: Duplicated pages when merging documents with identical page content streams but different per-page Resources.

Workaround: Use the RadFixedDocument.Merge() method instead of the PdfStreamWriter.

Here is a sample structure of the signature: 

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

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.

PdfStreamWriter stream-copy page splitting performance is much slower than expected in some cases. When working with larger PDF files, the processing time can increase a lot and cause noticeable delays.

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