Set the print resolution.
void pdfPrintSetDPI(PDFHandle pdf, int hDPI, int vDPI)
This function sets the horizontal and vertical print resolution, in dots per inch (DPI).

The horizontal and vertical resolutions are typically the same. (There are exceptions, such as some chart printers.)

pdfPrintResetParams resets this to its default value, which is to use the driver's default resolution.

pdfPrintSetDPI(pdf, 300, 300);