Currently, PdfStreamWriter writes only PDF pages. If we implement API for merging multiple pages or whole documents we would be able to preserve links between pages (which are currently being corrupted). Merging whole documents would also allow preserving document properties (bookmarks, interactive forms, ...). For a more detailed list of the unsupported document properties you can refer to our documentation: https://docs.telerik.com/devtools/document-processing/libraries/radpdfprocessing/formats-and-conversion/pdf/pdfstreamwriter/features. We may also implement API for adding initial document properties from some existing PDF file.