Free SSL Certificate is issued and signed by a popular Certificate Authority (CA) such as Let's Encrypt, StartSSL, WoSign etc. While, Paid SSL Certificate is issued and signed by trusted Certificate Authority (CA) such as Comodo, GeoTrust, Symantec, RapidSSL, Thawte, GlobalSign, AlphaSSL etc..
You can get Paid SSL from directly through either trusted Certificate Authority or authorized SSL reseller (Reseller offers SSL certificates at up to 89% cheaper price)
Site owner gets the same level of encryption with free SSL or Paid SSL certificate. However, Free SSL Cert is issued for 30-90 days validity, while paid SSL Cert is issued for a period of 1-3 years.
Free SSL CA follows only domain validation method through verifying the identity of website owner before issuing the certificate, while Paid SSL CA follows in-depth Organization Validation or Extended validation method of an organization before issuing the certificate for the particular domain.
Free SSL is ideal for blogs and small websites. Whereas, Paid SSLs can help to improve customer's trust and conversion rates on websites and ideal for large enterprises or e-commerce business.
