It looks like you didn't submit police certificates, which are required from Pakistan, but I'm not sure if they are required from India.
Also, they do require a statement of purpose in which you explain why you want to study in Canada and why you don't want to go to any similar program in your home country. It's also a good idea to explain to them how a degree from Canada will enhance your employment opportunities in your home country.
The usual educational course that is preferred is: BA/BSc, MA/MSc, and then another MA/MSc or a PhD. From the Sheridan College website it looks like their programs are not accredited bachelor's programs but you can transfer from them to a university to get a bachelor's degree. So that is probably why they had an objection to your application. See the bottom of the page here:
http://www.sheridancollege.ca/Programs%20and%20Courses/Full-Time%20Programs/Programs%20A-Z%20Index/Mechanical%20Engineering%20Technician%20Technology%20-%20Design%20and%20Drafting%20-%203%20year.aspx
So given that you already have a diploma, certificate, and work experience in mechanical engineering, they probably didn't think it was necessary for you to get another diploma/certificate/work experience from Sheridan College. If you were applying for an accredited BA program or if you had explained what was different in this Sheridan College program compared to the programs/courses you've already done, they would probably have not refused the application.
