How to Disable the CTRL+P using javascript or Jquery?

You can't prevent the user from printing, but you can hide everything when the user prints the document by using simple CSS:

<style type="text/css" media="print">
    * { display: none; }
</style>

Updated fiddle.

If you would like to show the visitor a custom message when he/she try to print rather then just a blank page, it's possible with client side code but first wrap all your existing contents like this:

<div id="AllContent">
    <!-- all content here -->
</div>

And add such a container with the custom message:

<div class="PrintMessage">You are not authorized to print this document</div>

Now get rid of the <style type="text/css" media="print"> block and the code would be:

if ('matchMedia' in window) {
    // Chrome, Firefox, and IE 10 support mediaMatch listeners
    window.matchMedia('print').addListener(function(media) {
        if (media.matches) {
            beforePrint();
        } else {
            // Fires immediately, so wait for the first mouse movement
            $(document).one('mouseover', afterPrint);
        }
    });
} else {
    // IE and Firefox fire before/after events
    $(window).on('beforeprint', beforePrint);
    $(window).on('afterprint', afterPrint);
}

function beforePrint() {
    $("#AllContent").hide();
    $(".PrintMessage").show();
}

function afterPrint() {
    $(".PrintMessage").hide();
    $("#AllContent").show();
}

Code is adopted from this excellent answer.

Updated fiddle. (showing message when printing)

After much testings on various browsers, it is easier to intercept the keys when they are down (not pressed) because some of this "App integrated keys" are difficult to intercept with the "keypress" event.

I came up with this script that is sort of cross browser compatible (I didn't test for Microsoft's IE). Notice that the browsers return different codes for some keys. In my case I wanted to prevent Ctrl+P.

The key "P" on chrome is seen as e.keyCode == 80, on opera, it is e.charCode == 16, while on firefox it is e.charCode == 112

$(document).on('keydown', function(e) {
    if((e.ctrlKey || e.metaKey) && (e.key == "p" || e.charCode == 16 || e.charCode == 112 || e.keyCode == 80) ){
        alert("Please use the Print PDF button below for a better rendering on the document");
        e.cancelBubble = true;
        e.preventDefault();

        e.stopImmediatePropagation();
    }  
});

I used jQuery.