To add a PDF printer follow these instructions:
 1. Open the cups frontend ('http://localhost:631/') in your favorite
    browser
 2. Add a new printer
 3. Enter 'Name', 'Description', ... to your liking
 4. Select 'CUPS-PDF (Virtual PDF Printer)' as device
 5. The manufacturer should be 'Generic'
 6. The model/driver is 'Generic CUPS-PDF Printer (en)'