This article applies to Microsoft Edge version 77 or later. XML Forms Architecture (XFA), is a legacy format of forms that isn't supported in Microsoft Edge. Documentation related to Accessibility scenarios that currently aren't supported can be found on the Microsoft Accessibility Conformance Reports blog. A license is required for MIP. For more information, see this Microsoft 365 licensing guidance. Process isolation. PDFs opened from different web sites are completely process isolated. The browser doesn't have to communicate with any websites, or PDF files opened from another source. PDF browsing is secure from any attacks that plan to use compromised PDFs as an attack surface. Application Guard. With Application Guard, admins can set a list of sites that are trusted by their organization. If users open any other sites, they are opened in a separate Application Guard window that runs in its own container. The container helps protect the corporate network and any data on user's computer from being compromised.This protection also applies to any online PDF files that are viewed. Further, any PDF files that are downloaded from an Application Guard window are stored, and when needed, re-opened in the container. This helps keeps your environment secure not just when the file is downloaded, but through its whole lifecycle. For more information, see Application Guard. You can make Microsoft Edge the default PDF reader for your organization. To do this, follow these steps. Thank you for writing to Microsoft Community Forums. We understand the concern as you would like to change the default app for launching a PDF file. We’ll certainly assist you to set the Adobe Acrobat as a default app/program for PDF files. In this scenario, we would suggest you to perform these methods and check. Method 1: Change Default PDF Viewer in Windows 10Using File Explorer. Right-click on a PDF file. Click on Open with > Choose another app. A pop-up window will prompt you to choose your preferred software. Tick the Always use this app check box and click OK. Click on More apps to expand the list. Scroll down until you see the Look for another app in this PC link and click on it.