a lots of user are facing issue while using Mozilla Firefox ( recommended browser of E-Office) where while adding any new receipt from Browse & Diarize or Opening any File pdf ( it goes to download section of firefox and does not shows up in Eoffice Page) , suggesting to look up below settings in Mozilla App to avoid this scenario , Go to Options > Applications, then find the listing for Portable Document Format (PDF). Under the Action column, make sure it is set to  Open in Firefox