Here's the code to add some documents to print and print all the documents in the queue:
```
printer_tasks = PrinterTasks()
# Add some documents to print
printer_tasks.add_document("Document 1")
printer_tasks.add_document("Document 2")
printer_tasks.add_document("Document 3")
# Print all the documents in the queue
printer_tasks.print_documents()
```
This creates an instance of the `PrinterTasks` class called `printer_tasks`. The `add_document()` method is called three times to add three documents to the queue. Finally, the `print_documents()` method is called to print all the documents in the queue.