To enable the Export To PDF button in any entities there is a setting in CRM. Please find the steps with the screenshot to display the button on the Contact entity.
1. Change the Area to App Settings > Productivity tools > Convert to PDF.

2. Search Contact, by entering in Filter by entity name field, select Contact entity, and click on the Save button.

Note: After saving the setting, please log out the CRM and re-login once again to see the changes in the environment.
Change the Area to Sales > Contact where you can see the Export to PDF button on the Command bar on the contact record as shown in the below screenshot.

Hope this helps.
Thanks!