Hey  Harsh,

You can't get Allen booklets in pdf form.You will need to purchase hard copy.

You can buy booklets directly from Allen career institute by joining their DLPD program (for this just visit their official website) or by visiting to any of their centres physically or you can also purchase from e-commerce sites such as Amazon, flipkart etc

You may also get their old booklets on OLX!!

Hope,it was helpful