Reference letter from previous employer

[shubhramit]

I am in US and planning to file PR application. I have total more than 8 years of IT experience. I worked in a big indian IT company for more than 7 years. I don't have experience certificate (reference letter) from them. I have lots of proof such as appointment letter, annual salary revision letters, W2 forms, pay slips etc.
Is there any alternate document, I can submit for experience letter such as affidavits from co-workers?

Please help.