ExpertPdf.MergePdf by Outside Software Inc.

<PackageReference Include="ExpertPdf.MergePdf" Version="6.0.0" />

 PdfDocumentOptions

public class PdfDocumentOptions
This class encapsulates the options to control the PDF document rendering process. The PDFMerge class define a reference to an object of this type

This property controls the compression level of the rendered PDF document

This property controls the PDF page orientation

public PdfPageSize PdfPageSize { get; set; }

This property controls the size of the rendered PDF document