Install the Add-On from Marketplace :
Log into your Confluence instance as an admin.
Click the admin dropdown and choose Atlassian Marketplace.
Click Find new add-ons from the left-hand side of the page.
Locate Simple PDF Exporter for Jira via search.
Click Free Trial to begin a new trial or Buy now to purchase a license for Simple PDF Exporter for Jira.
Enter your information and click Generate license when redirected to MyAtlassian.
Click Apply license.