The intent of this page is to provide brief information on the status of viewing PDF documents in the browser via built-in support or via plugins. While not intended to be a comprehensive guide across all devices & browsers, as additional information is discovered or reported this page will be updated.
With the emergence of HTML5 technology there has been a dramatic shift in browser support away from the old 'NPAPI' style plugins. This includes previously popular plugins such as Adobe Flash & Reader, and QuickTime. Some browsers no longer supports NPAPI at all (Google Chrome) and others disable those types of plugins by default (Safari), although the user can re-enable them.
In regards to basic PDF viewer support, most browsers now have a built-in PDF viewer enabled by default. These PDF viewers may not support all of the features that the latest Adobe Reader DC plugin (NPAPI or ActiveX) supports.
Additional steps if a pdf file won't open:
Make sure that the pop-up isn't blocked.
If you're using Internet Explorer, try using Mozilla Firefox.
(Firefox) Increase your offline storage limit. From the Firefox Tools Menu, select Options. In the Options window, select the Advanced top-level tab. In the Advanced section, choose the Network tab. Locate the Offline Storage section and use the text box/spinner control to increase the value “of space for the cache.” 200 MB or greater is advised.