There is NO need to pay for one. You can instantly get a free credit report from all 3 major reporting agencies once per year via this website.
https://www.annualcreditreport.com/cra/index.jsp
There is NO way to get your credit report without inputting your SSN. The website is completely safe. Much safer than writing a letter and disclosing the SSN in the letter which can get lost in the mail.
You definitely have to put personal information and your SSN on that website to pull your credit reports. No other way to do it short of sending in a letter or calling in and disclosing your personal information.
I'd recommend the website.