To open online PDF files with the Foxit, do the steps below:
1. Choose File> Preferences > File Associations > Advanced, and check the check-box next to Include browser when setting default PDF viewer > click on OK to close the advance... dialog box.
2. Click on Make default PDF viewer button to set Foxit PDF Reader as the default PDF Viewer and apply the change.
3. Restart the Web Browser.
Note:Firefox,Google Chrome and Opera these browsers all no longer support the NPAPI style plugins,so Foxit PDF plug-in can not work in Firefox(version 52 and above),Google Chrome(version 45 and above) and Opera(version 12.17 and above) anymore.