Set the horizontal and vertical scale factors.
void pdfPrintSetScale(PDFHandle pdf, double xScale, double yScale)
This function sets the horizontal and vertical scale factors, where 1.0 means actual size, 0.5 means half-size, 2.0 means double-size, etc.

pdfPrintResetParams resets this to its default value, which is to print at actual size (xScale = yScale = 1) if the PDF page fits on the paper, and to shrink larger pages to fit (xScale = yScale < 1).

pdfPrintSetScale(pdf, 0.75, 0.75);