Change in support for Acrobat and Reader plug-ins in modern web browsers
Adobe Acrobat and Acrobat Reader run as a plug-in to display PDF files in a web browser. For Google Chrome and Mozilla Firefox, the plug-in is based on the Netscape Plug-In API (NPAPI) technology. For Microsoft Internet Explorer, the plug-in is an ActiveX based plug-in. Support for such plug-ins is changing for some modern web browsers.
Modern web browser recent developments
Google announced that in April 2015 NPAPI plug-in support is disabled by default in the Google Chrome web browser with an override capability for advanced users. In September 2015, NPAPI support in the Google Chrome web browser was removed entirely.
For Windows 8, the Windows Modern UI Browser does not use plug-ins.
Windows 10 ships with both IE 11 and the new Edge browser. The Edge browser is the default browser, and IE 11 is available to support legacy workflows. The Edge browser does not have any support for ActiveX plug-ins:
What if I want to continue using a web browser that does not support NPAPI but still use Reader?
Web browsers have preferences that enable viewing a PDF in Adobe Reader. For example, you can configure Chrome to use Reader via its System Viewer preference.
What if an enterprise wants to support browser-based workflows using Reader?
Enterprises may use a browser that supports the ActiveX plug-in, such as Microsoft’s Internet Explorer.
Adobe is committed to continuing support for IE with ActiveX and web browsers that support NPAPI.
PDF display issues with web browsers that support NPAPI plug-ins
If you are experiencing issues with a web browser the still supports NPAPI plug-ins, see Configure browser to use the Adobe PDF plug-in and Display PDF in browser | Acrobat, Acrobat Reader.