Page orientation

Hi everyone.

I Create addin for Autodesk Revit, and use PDFCreator as virtual printer. I need print pages in vertical or ladscape orientation. I use autosave to prevent user see PDFCreator dialog. So i need set printer option in code.
I find “Papersize” key in windows register and pass papersize there (A4,A0 etc.) But i unable find parameter to set page orientation. Help me plz.