For paperwork like PDFs, there’s no way to put canonical tags while in the page header because there is not any web page area. In these scenarios, you’ll must use HTTP headers to set canonicals. What this means is other position factors may perhaps override it and rank One more https://addons.prestashop.com/en/seo-natural-search-engine-optimization/31857-automatic-google-rich-snippets-json-ld-open-graph-seo.html