When the Office Web Apps were launched in June, you could print using the Word Web App viewer but not the editor. After sifting through much customer feedback about this glaring ommission, Microsoft has rectified the situation by adding the print facility to the editor too.
The process for printing in the Word Web App is very much the same as that used in the desktop version of Word 2010: click the File tab > Print.
When you click on Print, the print dialogue window that you are probably already used to seeing opens for you to make selections such as:
When you have made your selections, click OK and the document will be sent to the printer.
The print facility is also available in the PowerPoint Web App (in both Edit and View modes), but is missing from the Excel Web App.