Converting a .tiff to a .pdf in Ubuntu

For some reason, my CUPS under Ubuntu 7.10 refuses to print-to-pdf. I've tried everything I know (not much)...and probably broke a lot of stuff along the way.
But I found an easy way to do it from the command line.

1. Scan the item to a .tiff file in a known location (for example, save it to the Desktop)
2. Open a terminal:
   

   convert -density 300 -units PixelsPerInch Desktop/scanned_file.tiff converted_file.ps
   ps2pdf -s PAPERSIZE=letter converted_file.ps final_output_file.pdf
   rm scanned_file.tiff converted_file.ps