When I run my Windows 8.1 App, the annotation toolbar icons are missing. I tried Windows 10, and it was fine, and also the PDFNet SDK samples work fine on Win 8.1
It appears the problem is a glitch in Windows 8.1, where because the tools are used in an intermediate project, the resources (custom.ttf) seem to not be accessible at runtime. This same setup works fine on Windows 10, just not on Windows 8.1. This works in our samples, and I suppose most of our customers, because the tools are used directly.
Note, the icons are in the PDFViewCtrlTools project, in Controls → Resources → custom.ttf
Fortunately the tools project is open code for you. The easiest solution would be to create a folder inside the Example.WinRT project called Tools and simply drag all the source code into that project. You will have to manually change the resource paths. The other option is to only move the AnnotationToolbar over, along with the font file.