For macOS and iOS
Beginning with iOS 7 it is pretty easy to add the fonts Chords and Scales to your iPad/iPhone and use them in Pages, Keynote and other eligible apps such as Graphic, PDF Expert and Pixelmator to name a few. To take advantage of Drag and Drop in iOS 11 upload the Chords and Scales library to your iCloud Drive using your iPad's Split View and Slide Over features. See also blog post.
Adding neck diagrams to PDF lead sheets on the iPad
It comes in handy that quite a few PDF reader apps for iOS let you annotate text notes and hence Chords and Scales neck diagrams to your PDF lead sheets.
- open a PDF lead sheet in an eligible PDF reader app
- reveal the annotation toolbar and add text notes to the pdf
- choose the font families Chords and Scales and select font size and font color
- create chord diagrams, scale diagrams, arpeggio diagrams or blank diagrams direct in the pdf document
- tap Done