embed pdf in web page drupal file field formatter

Simpler newer alternative: PDF To Canvas File Field Formatter | Drupal.org

Overview, don’t miss PDF module at the top: Comparison of PDF viewer modules | Drupal.org

Using only an iFrame works, as documented here: https://webtech.training.oregonstate.edu/faq/how-do-i-embed-pdf-file-osu-drupal-node

Now that i think of it, probably the ideal is an embed that falls back to a link if the browser does not support it— which is most mobile browsers, it seems, and probably the experience of opening in its own app (which i hope mobile phones all have?) is better than embedding in a web page.