InDesign Document Size for iPad

Creating properly sized content for the iPad can be easy, but there are some difficulties.

The first one is an obvious one: landscape or portrait ?

You can't lock or force the rotation of the iPad or design in a browser view. So the view will switch to what orientation the user prefers, scaling it to fit the screen's size and adding black margins to either sides. Hopefully users will understand the best orientation of your design, and rotate their iPad accordingly.

The next one is a numbers game: output resolution.

Depending on the setting of the physical size of your page or whole document (in pixels or inches), the export will vary the output resolution of all imagery. So if you're designing at a 4 x 3 cm size with the output set to 96 dpi (in the Advanced panel of the Publish Online dialogue), all imagery will look very sloppy ! Changing the design's size to 20 x 15 cm immediately renders more pixels into the output, giving a much better viewing experience.

The design in InDesign, consisting of a yellow background, a simple line of text, a hi-res image with a shadow, an opaque star shape (vector), and a semi transparant pink blob (vector).

At 96 dpi, elements in the the 4 x 3 cm document size will consequently be rendered (flattened, rasterised) into very coarse pixels. The difference between 96 and 144 dpi doesn't improve it enough. What also surprises, is that even vector-based and fully opaque elements need to be rasterised, and that overlaying bounding areas of different types of elements can yield different raster tints !

But changing the document size to 20 x 15 cm immediately has a bigger an better impact:

So create or scale your design to the proper physical size, or find a good average when you need to cater a wider scale of device sizes (from iPad mini to a large pro). The original iPad was quite content with 1024 x 768, but newer models range to almost three times that number of pixels.

And last but not least: these Publish Online views are always within a browser screen, and on an iPad you can't switch to full-screen. (ePubs can be viewed full-screen, within iBooks). So you don't get the full width/height of the screen.

If you want to set the document up with Pixels as the measurement unit and the target is the iPad Pro, then the size should be the iPad Pro’s 2732 x 2048. In that case the listed Effective resolution of any placed images only has to be 72ppi or higher in order to get the best quality on the iPadPro.

If you want to work in Inch units rather than Pixel units, divide the iPadPro's 2732 pixel width by the document's Inch width in order to get the optimal ipad resolution. So images placed in a 10" x 7.5" document would need a minimum Effective res of 273ppi in order to take advantage of the iPadPro’s full resolution.