Document stays in memory when using PdfReader.Open about pdfsharp HOT 5 CLOSED

            Thread.Sleep(5000);
            
            using (PdfDocument pdfDocument = PdfReader.Open("a.pdf", PdfDocumentOpenMode.Import))
            {
                pdfDocument.Dispose();
            }
            Console.WriteLine("pdfDocument should be closed and removed from memory");
            Console.ReadKey();

GCSettings.LargeObjectHeapCompactionMode = GCLargeObjectHeapCompactionMode.CompactOnce;
GC.Collect();

            Thread.Sleep(5000);
            
            for(int i = 0; i < 10; i++)
            {
                using (PdfDocument pdfDocument = PdfReader.Open("file.pdf", PdfDocumentOpenMode.Import))
                {
                    pdfDocument.Dispose();
                }

            }
            GCSettings.LargeObjectHeapCompactionMode = GCLargeObjectHeapCompactionMode.CompactOnce;
            GC.Collect();
            Console.WriteLine("pdfDocument should be closed and removed from memory");

            Console.ReadKey();