Add support to extract viewer preference

fpdfsdk/src/fpdfview.cpp

Index: fpdfsdk/src/fpdfview.cpp
diff --git a/fpdfsdk/src/fpdfview.cpp b/fpdfsdk/src/fpdfview.cpp
index a5ba796158705184300e27a699a48ce64c4b02f6..c088c688529973be71cedafe228106861d559f8d 100644
--- a/fpdfsdk/src/fpdfview.cpp
+++ b/fpdfsdk/src/fpdfview.cpp
@@ -866,6 +866,30 @@ DLLEXPORT FPDF_BOOL STDCALL FPDF_VIEWERREF_GetPrintScaling(FPDF_DOCUMENT documen
 	return viewRef.PrintScaling();
 }
 
+DLLEXPORT int STDCALL FPDF_VIEWERREF_GetNumCopies(FPDF_DOCUMENT document)
+{
+    CPDF_Document* pDoc = (CPDF_Document*)document;
+    if (!pDoc) return TRUE;
+    CPDF_ViewerPreferences viewRef(pDoc);
+    return viewRef.NumCopies();
+}
+
+DLLEXPORT FPDF_PAGERANGE STDCALL FPDF_VIEWERREF_GetPrintPageRange(FPDF_DOCUMENT document)
+{
+    CPDF_Document* pDoc = (CPDF_Document*)document;
+    if (!pDoc) return NULL;
+    CPDF_ViewerPreferences viewRef(pDoc);
+    return viewRef.PrintPageRange();
+}
+
+DLLEXPORT FPDF_DUPLEXTYPE STDCALL FPDF_VIEWERREF_GetDuplex(FPDF_DOCUMENT document)
+{
+    CPDF_Document* pDoc = (CPDF_Document*)document;
+    if (!pDoc) return FALSE;
+    CPDF_ViewerPreferences viewRef(pDoc);
+    return viewRef.Duplex();
+}
+
 DLLEXPORT FPDF_DEST STDCALL FPDF_GetNamedDestByName(FPDF_DOCUMENT document,FPDF_BYTESTRING name)
 {
 	if (document == NULL)