How to do pdf password protected in node js

Today i have a requirement in my node js project to do pdf password protect. So any one open that pdf he must be enter password then he can view the pdf content. I am doing a lots of googling but i didn't get the proper solution of it. There is no module of node which i can use to protect my pdf. So finally i write a command and i execute it in node js. Actually this is a very easy after writing few lines you can do it. Below is my code and method of uses.

This is my code :

var exec = require('child_process').exec;
var pdfsourcepath = '../client/app/loanpdf/loan_21213131.pdf'; // This is pdf path with pdf name with out encription.
var pdfdestinationpath = '../client/app/loanpdf/loan_encripted_21213131.pdf'; // This is encripted pdf path with pdf name.
var password = "test123";  //This is your password to decript pdf.
var command = 'qpdf --encrypt '+password+' '+password+' 40 -- '+pdfsourcepath+' '+pdfdestinationpath;

exec(command,
function (error){
 if (error !== null){
 console.log('exec error: ' + error);
 }else{
console.log('Your pdf is encripted successfully.');
 }
}
);


Dependency of this code : 

1- You have to install qpdf first on your server by run this command 

sudo apt-get install qpdf

2- Don't forget to inclule the "child_process" library on the top of your file. By default is it comes with the bundled of node.js. So you don't need to install it.

var exec = require('child_process').exec;

Output of this code like below screen shot -

If you having any problem while using this code or you like this post don't forget to leave a comment below i will reply you back with your.

Chears
Happy coding :)