Hi Aditya. MGMAT free pdfs? Do you mean copies of the MGMAT strategy book series in digital format?
You need to support the strategies you are learning from the MGMAT books
with practice on official problems. So, you need the Official Guide 13th
edition (or 12th edition) at a minimum.
I recommend you check out my guide to self-study: GMAT Clarity (amazon link)
. It will save you an enormous amount of time in your prep and help you score higher than you would without professional guidance.