How to instruct Chrome to download PDF rather than (pre)view in browser?

You could use the download property in your link (anchor) like so:

<a href="some/path/somefile.pdf" download target="_blank">download PDF file</a>

This would force download in the browsers, which support it (Chrome, Firefox and Opera). However, it is not currently supported in IE or Safari as per this link

Source: https://stackoverflow.com/questions/3802510/force-to-open-save-as-popup-open-at-text-link-click-for-pdf-in-html

I am not sure whether it is possible through custom code in website. As far as I know it is totally depends on user setting in their chrome browser.

Basically when you type : chrome://plugins/ , It will list you chrome plugins and If user disable plugin called : Chrome PDF Viewer , then only chrome will ask to download PDF otherwise PDF will open there automatically.