Printing from command line prints blank page

Hi

I want to use PDF Creator to create a .pdf-file from a .rtf-file.

Printing from the GUI works but if I want to print the file in the command-line it always creates a blank, whithe pdf with the size of 2.53KB.

The command-line I use: pdfcreator.exe /IF"U:\Rechnung.rtf" /OF"U:\Rechnung.pdf"

Is there any mistake I made in the command-line or what else can I do?

Thank you for your help.