PDF hosted in Act-On using PDF embed API from Adobe. Source code and demo on https://documentcloud.adobe.com/view-sdk-demo/index.html#/view/FULL_WINDOW/Bodea%20Brochure.pdf

PDF url is https://marketing.marketingguys.nl/acton/attachment/7349/f-3966916d-6e97-4963-b48e-7b1b90f069d0/1/-/-/-/-/Whitepaper%20Marketing%20%26%20Sales%20alignment.pdf

Below iframe setup to show that pdf works

Below setup using PDF Embed API: Works!