code: protected boolean matches(PDF pdf) {
          try (InputStream inStream = pdf.openStream()) {
              final PDDocument doc = PDDocument.load(inStream);
              return matchesPDF(doc);
          } catch (IOException e) {
              LOG.debug("Could not load PDF document", e);
              return false;
          }
      }
docs: Is invoked by the matches method when the type of the target object is verified. Override this method to add
  verifications on the raw data instead of a loaded document.
  
  @param pdf
  the handle for the PDF data
  
  @return <code>true</code> if the pdf document is a valid PDF document.