vDPI

Set the vertical print resolution.
[read/write property] vDPI([out, retval] int *dpi) vDPI([in] int dpi)
This property sets the vertical print resolution, in dots per inch (DPI).

Similarly, the hDPI property sets the horizontal print resolution.

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

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

VB6:
pdf.hDPI = 300 pdf.vDPI = 300
hDPI
resetParams