I just learnt something new a little while ago. I was thinking, this could be something other people might need as well. Thanks to some bad UI from IRCTC ofcourse, this is fairly undiscoverable.
More recently, I have seen people (and Ticket Checkers in trains) recognize the importance of saving paper and just showing an SMS for PNR confirmation and a photo-ID. So I wanted to do the same thing for an upcoming rail trip. However, I did realize I had deleted the SMS from IRCTC.
There is a way to get IRCTC to resend you the SMS (you can do this upto 5 times for a PNR).
1. Login into IRCTC
2. Get into Booking History
3. Choose your ticket of choice and click on Get SMS again.
Voila. Save paper. Save trees.