Is Paperpal's Reference Checker free to use, or does it require a paid plan?

Paperpal’s Reference Checker is a paid feature. You will need to upgrade to a Prime or Pro plan to get access to Reference checks and unlock higher limits on our entire suite of research, writing, and submission tools.  
 
As a Prime user, you get 10,000 words of Reference Checks/month. This limit resets every month with your Prime subscription. To check larger files, you can upgrade to the Pro Plan or buy a one-time add-on.   
 
With the Pro Plan, you get up to 30,000 words per month. This limit will also reset every month. To run additional Reference Checks, you can purchase one-time add-ons. Add-on words come in packs of 10,000 words and can be used across Plagiarism and Reference Checks. They remain valid for 30 days from date of purchase.