How do I know if I am on the free or paid version of Plug in SEO?
Go to your Shopify admin > Apps > Plug in SEO.
In Plug in SEO, look for the 'SEO Tools' in the right column of your dashboard.
If you are prevented from accessing the SEO Tools then you are on the free version. If you can access the 'Page Titles and Descriptions' and the 'JSON-LD Structured Data' features then you are on the plus version.