Down at the bottom of every Moodle page is "Moodle Docs for this page", my trainer's can't see this button. Does anyone know why this might be happening? It has to have something to do with the roles.
Please check that you have mention the link here Moodle docs document root from Settings > site administration > Appearance > Moodle Docs.
After that please check this capability Show links to offsite docs: Allow for trainers from Settings > site administration > Users Permission > Define roles.