code: protected void carriageReturn() {
          // the arraylist with lines may not be null
          if (lines == null) {
              lines = new ArrayList();
          }
          // If the current line is not null
          if (line != null) {
              // we check if the end of the page is reached (bugfix by Francois Gravel)
              if (currentHeight + line.height() + leading < indentTop() - indentBottom()) {
                  // if so nonempty lines are added and the height is augmented
                  if (line.size() > 0) {
                      currentHeight += line.height();
                      lines.add(line);
                      pageEmpty = false;
                  }
              }
              // if the end of the line is reached, we start a new page
              else {
                  newPage();
              }
          }
          if (imageEnd > -1 && currentHeight > imageEnd) {
              imageEnd = -1;
              indentation.imageIndentRight = 0;
              indentation.imageIndentLeft = 0;
          }
          // a new current line is constructed
          line = new PdfLine(indentLeft(), indentRight(), alignment, leading);
      }
docs: If the current line is not empty or null, it is added to the arraylist
  of lines and a new empty line is added.