The shortest and free way that I can think of is this:
1. Download and install Inkscape (free; about 35Mb).
2. Download and install one of the free pdf writers (like cutepdf or dopdf or bullzip pdf - about 10Mb)
3. Open Inkscape, open the .cdr file from File >> Open
4. Print the file from File >>> Print. Choose the pdf writer as your printer, and you are good to go.