I have found this: (i am now trying to print from a pdf with 90 pages) - somehow it adds one to the page no.
var pp = this.getPrintParams();
pp.interactive = pp.constants.interactionLevel.full;
pp.printRange=[[1,89],[2,89],[3,89]];
this.print(pp);
Result:
1,89,2,89,3,89
which gives 2 - 90 ; 3 - 90 ; 4 - 90 in acrobat's print dialog box! Why?