When the PDF image format was first made available for DPS articles, the format was limited. Most importantly, interactive overlays were not supported in PDF-based articles, so most designers stuck with the JPG/PNG image format unless they wanted users to be able to pinch & zoom on a page.
With the v18 release of the tools, that changed. Now, all interactive overlays in PDF articles work just as well as they do in JPG/PNG articles.
With the new retina display iPad, using the PDF format has now become the recommended choice for image format. PDF articles are smaller than JPG/PNG articles, and vector content is maintained, resulting in improved scaling. However, there are still some differences between the PDF and JPG/PNG image formats that you should be aware of.
If you’re in a hurry, here’s the executive summary.
- For iPads, we recommend creating 1024×768 folios with articles in the PDF image format. PDF results in smaller article size and maintains vectors. To avoid rasterizing text in slideshows and scrollable frames, you can choose Vector in the Folio Overlays panel. These articles in PDF image format look great on both SD and HD iPads.
- For multi-issue viewers, you can create separate SD and HD folio renditions so that the 1024×768 folio appears on the SD iPad and the 2048×1536 folio appears on the HD iPad. This approach is useful if you want to use PNG or JPG image format instead of PDF. The easiest rendition approach is to create 1024×768 source documents and use these as the basis for both the 1024×768 folio and the 2048×1536 folio. You might want to show/hide layers for certain overlays such as pan & zoom images.
- For single-issue viewers, you cannot create renditions. Create a single 1024×768 folio with PDF image format. For details, see Creating multi-rendition articles for iOS devices.