Computer Configuration > Administrative Templates > Google Chrome > Content settings
Both
HKLM\Software\Policies\Google\Chrome
Setting this policy allows the domains listed to access file:// URLs in the PDF Viewer. Adding to the policy allows the domain to access file:// URLs in the PDF Viewer. Removing from the policy disallows the domain from accessing file:// URLs in the PDF Viewer. Leaving the policy unset disallows all domains from accessing file:// URLs in the PDF Viewer. Example value: example.com google.com