CEWP Print Button with Code to print SharePoint form?

Question 1

Inspired by this InfoPath print button, one solution would be to grab the contents of your CEWP and create a new window that only contains those.

var patt = /**your CEWP ID here***/g;
var alldivs = document.getElementsByTagName('div');
var printpageHTML = '';
for(var i=0; i<alldivs.length; i++){
  if(patt.test(alldivs[i].id)){
    printpageHTML = '<HTML><HEAD>\n' +
      document.getElementsByTagName('HEAD')[0].innerHTML +
      '</HEAD>\n<BODY>\n' + 
      alldivs[i].innerHTML.replace('inline-block','block') + 
      '\n</BODY></HTML>';
    break;
  }
}
var printWindow = window.open('','printWindow');
printWindow.document.open();
printWindow.document.write(printpageHTML);
printWindow.document.close();
printWindow.print();
printWindow.close();

Fixed: removed escaping for HTML characters.

Question 2

Simple print functionality:

<input id="printpagebutton" type="button" value="Print this page" onclick="printpage()"/>

<script type="text/javascript">
function printpage() {
    //Get the print button and put it into a variable
    var printButton = document.getElementById("printpagebutton");
    //Set the print button visibility to 'hidden' 
    printButton.style.visibility = 'hidden';
    //Print the page content
    window.print()
    //Set the print button to 'visible' again 
    //[Delete this line if you want it to stay hidden after printing]
    printButton.style.visibility = 'visible';
  }
 </script>