duplex

Set the duplexing mode.
[read/write property] duplex([out, retval] int *type) duplex([in] int type)
This property sets the duplexing mode. Allowed values for type are: Note that all of these values are read-only properties on the COM component, so you'll need to use pdf.duplexVert, etc.

resetParams resets this to its default value, which is duplexDefault.

VB6:
pdf.duplex = pdf.duplexVert
duplexDefault
duplexVert
duplexHoriz
simplex
printerSupportsDuplexing
resetParams