PrintPaperHandling duplex hint into a Windows printer DEVMODE.function SetPdfPrintPaperHandlingDevMode(var DevMode: TDeviceMode; PrintPaperHandling: TPrintPaperHandling): Boolean;
SetPdfPrintPaperHandlingDevMode converts the PDF viewer-preference duplex enum into the Windows printer-driver fields used by GDI print jobs.
phSimplex sets DEVMODE.dmDuplex to DMDUP_SIMPLEX.phDuplexFlipShortEdge sets DEVMODE.dmDuplex to DMDUP_HORIZONTAL.phDuplexFlipLongEdge sets DEVMODE.dmDuplex to DMDUP_VERTICAL.For mapped values the function also marks DM_DUPLEX in DEVMODE.dmFields and returns True. For phUndefined it returns False and leaves the supplied DEVMODE unchanged.
if SetPdfPrintPaperHandlingDevMode(DevMode, Pdf1.PrintPaperHandling) then
ApplyPrinterDevMode(DevMode);