Dear Hasse,
What is the target selected?
According to the message, it seems the Index target is selected.
The Index target is a dummy target and should not be used. It always throws the error you mention.
Please select the Build target to compile only, and the All target to compile and upload.
About the quality of the images, the full quality PDF is 6 GB. I'm obliged to reduce the size because the host for the website limits the size of the files. Uploading larger files would require a non-free plan.
Please don't consider my user manual is an introduction to Xcode. There are excellent books about Xcode: for example, I recommend Xcode 4 Unleashed by Fritz F. Anderson I've purchased thanks to contributions.
The user manual I wrote only focuses on how to use the template. Xcode, like all other professional IDEs —to name a few: Visual Studio, Eclipse, NetBeans, Qt, ...—, has a steep learning curve. The magic of the Arduino IDE relies in its instant plug-and-play gratification.
As a matter of fact, I'm still using the Arduino IDE when I don't need the power of Xcode.