Make sure that the Adobe Reader plug-in is enabled in your browser settings.
Go to 'Settings', select the 'Show advanced settings' link, then, 'Privacy content'. Under 'Plug-ins', select the 'Disable individual plug-ins' link, then enable 'Adobe Reader'. Don't forget to save your settings.
You can also save your statement as a PDF, by selecting the 'Print' option - simply change the destination to 'save as PDF', and select the save button.