You can do this with javascript:
try {
// save a copy of original document
var newName = this.path;
var filename = newName.replace(".pdf","_Original.pdf");
this.saveAs(filename);
for (var i = this.numPages - 1; i >= 0 ; i--)
{
if (i % 2 != 0)
{
this.deletePages(i,i);
}
}
}...