title: Swift PDFView issue: .notdef: no mapping
body: <p>I get odd error messages with PDFView from PDFKit.
  In some instance I get</p>
  <p>non-isolated groups aren't supported.
  Mutating glyph 1 (code 32) in ULBEWJ+MinionPro-Regular.</p>
  <p>In another instance I get the message:
  .notdef: no mapping.</p>
  <p>In most PDF's I display I get no error messages.
  The same for all PDFs is that they're all shown correctly in simulator.
  Does this has something to do with UTF?
  Any idea how to fix those error messages?</p>