cannot handle iref streams pdf merge

1) Add Drag and drop feature
2) When trying Append 2 pages on single Page and create one pdf containing 492 pages: from a pdf filea to cannot handle iref streams pdf merge: The current implementation of PDFsharp cannot handle this PDF feature introduced with Acrobat 6
3) Append 2 Pages on Single Page and create One PDF. From big pdf file so that to shrink the number of pages to half.