Firefox issue:
Starting in Firefox 19, PDF files will display by default in a built-in viewer. This viewer does not yet support all of the features of the Adobe viewer, and may also have some bugs. Other than changing viewers, as described in the following article, I’m not sure what to suggest.
Source : https://support.mozilla.org/en-US/questions/977657
Options
https://support.mozilla.org/en-US/kb/disable-built-pdf-viewer-and-use-another-viewer
