It is very tough to get all details on one letter. So i got two letter
Experience letter ( show date i worked and job titile )
additional letter ( show responsibility and no of hr in week)
Offer letter ( salary and benefits)
Tax statement ( proof of paid tax)
Is above documents are enough to show previous work experience ??????????
also add ur salary slips and bank account statements showing ur salary credit in ur account to make ur case strong. provide the companies details including e-mail id and contact number on ur experience letter.