handle PDF download visibility

Author: OlivierJourdan

www/en/modules/ROOT/pages/index.adoc

@@ -14,4 +14,8 @@ NOTE: This page is the entry point of the course.
 
 * https://labviewcommunitytraining.github.io/Website-Course-Template/course-material.zip[Course material zip]
 
-* {site-url}/{page-component-name}/{page-component-version}/{page-component-name}.pdf[PDF version of the course]
+// do not include the PDF download link in the PDF itself
+
+ifeval::["{backend}" != "html5"]
+* {site-url}/{page-component-name}/{page-component-version}/{page-component-name}.pdf[PDF version of the course]
+endif::[]