I've been working a lot in recent weeks with the upcoming Adobe Digital Publishing platform for publishing content from InDesign to the iPad. I'll certainly be talking more about this in future blog posts as the solution becomes public. (In the meantime, see the Adobe Digital Publishing Blog for more information on what some "bleeding edge" customers are doing with it.)
If you're designing a document or image that is ultimately going to be viewed on the iPad, either with the Adobe Digital Publishing platform, a PDF reader, or some other method, how large should you create the document or image, and how do you preview your results?
The iPad screen is 9.7" diagonal, displaying 1024 x 768 pixels. This works out to 132 pixels per inch. So all you need to do is create a 1024 x 768 pixel image or page in Photoshop, Illustrator or InDesign. If you're using an older version of Illustrator or InDesign that doesn't support measuring in pixels, use points instead, and it will work out perfectly.
How can you preview what your file will look like without moving it to an actual iPad? If you're lucky enough to have a newer 15" Apple MacBook Pro with the optional High Resolution (1680 x 1050 pixel) display option, or a newer 17" Apple MacBook Pro with the standard High Resolution (1920 x 1200 pixel) display, you're in luck. These displays run at almost exactly the same resolution as the iPad. This means that you can create an image or layout in Photoshop, Illustrator or InDesign, and view it at 100% size on either of these displays to get a preview that is very, very close to how it will display on an iPad!