Hello Xpressentry, you have already letter head means ??
Please don't do any things means bypass to HR or your Manager. Kindly note that they will contact your company or even your Manager as well. Yesterday I got the reference letter from my previous employer and I have had company letterhead also but I prefer to go HR to provide me reference letter. In future if they will contact your company and if any mis interpretation observe then you will be in big trouble.
Option 1:- Ask HR to and get reference letter on company letterhead. First send mail to them that I need reference letter on letterhead,. If all things are good then it's Great for you. But this things should on letter head your job duties as per your NOC, Time period, weekly hours of your work, last designation at the time of left company, your salary package, company seal and business card whoever signed on reference letter if possible to collect also.
Option 2:- if your HR to refuse to provide reference letter on letterhead then tell them to reply my mail that we couldn't provide you on company letterhead. Please note this mail should also attach your application while you are going to send CIC. Same letter copy print on A4 page and sign by your colleague or Manager but don't forget to do company seal and collect their Company ID card or business card .Lastly , notarised this letter.
If you go to option 2 then your have to show your appointment letter (employer contract), salary slips, company experience letter. This things need to attach and also need to add letter of explanation in this.
I personally think that please go to option 1 it's good to show only one letter rather than more letter.
Hope it helps.