PDF does not download on iOS devices

I have tested with file stored in WP Media AND stored at Amazon S3. Image widget in sidebar has image of document cover, with link to the file. Downloads fine on computer. On iOS device the image is displayed in the lightbox but the PDF does not download. Site: http://damesdugolfdurochat.fr/ File: https://s3.us-east-2.amazonaws.com/cupexpublic/pdf/2019-Rules-Golf-FR.pdf