Apple has updates its three iWork apps for the iPad: Pages, Numbers and Keynote to add support for iOS 4.2. The updates add wireless printing via AirPrint and support for iOS 4.2 multitasking and Numbers also adds a print preview feature to allow users to adjust how a sheet will print across multiple pages. The PDF export from Numbers will also respect any pagination settings created in the print preview. Numbers users can also now enter formulas…