Sorry for the delayed response and inconvenience caused. As per the description above, Outlook 2016 is crashing while sending any PDF file as an email, Is that correct?
Please check for any pending updates of Acrobat from help>check for updates, reboot the machine after the installation of updates.
Make sure you are signed in Adobe Send and Track plugin: Adobe Send & Track for Outlook, Acrobat And this is supported and tested with Outlook 32 bit platform only: Send and track large files easily | Adobe Send & Track
Is Acrobat DC installed on your computer? What is the dot version of Acrobat installed, to identify refer to Identify the product and its version for Acrobat and Reader DC
Repair Outlook once from Control Panel>Program and Features>Locate Outlook 2016>Right Click>Choose to Repair. Reboot the machine after repair and see if this brings any difference.
Let us know how it goes and share your findings.