https://github.com/mozilla/pdf.js/issues/6397#issuecomment-164954332 Would have been a lot easier to find had there been an assertion checking that string16 didn't go out of bounds of the 16bit number.

PV: "PageVisible",
  PI: "PageInvisible",
  K: "Keystroke",
  F: "Format",
  V: "Validate",
  C: "Calculate",
};
const DocumentActionEventType = {
  WC: "WillClose",
  WS: "WillSave",
  DS: "DidSave",
  WP: "WillPrint",
  DP: "DidPrint",
};
const PageActionEventType = {
  O: "PageOpen",
  C: "PageClose",
};
const StreamType = {
  UNKNOWN: "UNKNOWN",
  FLATE: "FLATE",
  LZW: "LZW",
  DCT: "DCT",
  JPX: "JPX",
  JBIG: "JBIG",
  A85: "A85",
  AHX: "AHX",
  CCF: "CCF",
  RLX: "RLX", 
};