Printing: Replace PDFtoPrinter with PdfiumViewer

Elwig/Documents/Document.cs

@@ -153,7 +153,7 @@ namespace Elwig.Documents {
 
         public async Task Print(int copies = 1) {
             if (PdfPath == null) throw new InvalidOperationException("Pdf file has not been generated yet");
-            await Pdf.Print(PdfPath, copies);
+            await Pdf.Print(PdfPath, copies, DoublePaged);
         }
 
         public void Show() {