anchor.diff:      PAGE_FIT,
       PAGE_WIDTH,
       _0_50,          // <2>
  +    _0_75,
       ...
       _4_00;          // <3>
   }
  
positive.code: To fit their particular screen, they may want to adjust the zoom level and/or height of the panel.
  It would however be very tiresome of the next document viewed reset to the defaults specified in the `@PdfJsViewer`.
  
  Related, if a user were to view a first document and navigate to a page 2 or 3, then move to second document, and then back to the first, it would again be annoying if the user had start back at page 1 and navigate once more to a different page.
  
  To support these two use cases the component therefore provides an optional SPI service as a plugin point.
  Implementations of this SPI service can provide hints (`Advice`) which override the defaults of the `@PdfJsViewer` annotation.
  
  The SPI is defined as:
  
negative.code: [source,java]
  ----
  @PdfJsViewer(
      initialPageNum = 1,
      initialScale = Scale._0_75,
      initialHeight = 600
  )
  public Blob getBlob() {
      return this.blob;
  }
  ----
  
  
  The `Scale` enum corresponds to the scale drop-down in the view, and is defined as:
  