Comment 23 for bug 503372

There's a workaround, but it's another program - Okular.

In synaptic install Okular. Once Okular is open press "F7" to turn off the sidebar. Then go to "Settings", "Configure Okular", and remove the check next to "Show hints and info messages."

Next, in Nautilus right-click on any pdf. Click "properties", then "Open with", and click the radio button next to Okular and close.

Finally open up firefox, go to "edit", "preferences", and click on "applications." Next to "PDF document" pull down the menu and click "use other." Click the pencil at the top left and paste into the new textbox "/usr/bin/okular".

Now any PDF you open in firefox, nautilus, or anywhere else should open in Okular without the sidebar.

As a bonus you can use reviewing tools, which are a handy way to mark-up a pdf.