What mozprintCallback experimental API do?
mozPrintCallback – A new callback for canvas that is executed during the printing process. This callback can access the printing canvas context and perform any calls that are normally done to a 2D canvas context. When the callback is finished with rendering it must call printState.done() to tell the printing code to advance. The benefits of this approach are: 1) we don’t have to try and render every page before print, 2) the output gets rasterized later in the printing process where it should be. (This is not available for all platforms yet).
At present you can’t see the print button in Aurora and other earlier versions as mentioned above this experimental API is currently available in Firefox 18 nightly build only.
One more surprise change we spotted in nightly for Pdf.JS is Download button on UI works well with new download panel icon. When you try to download PDF by clicking on that button animation shown moving of download icon from UI on to green colored new download manager icon on toolbar indicates file being downloaded and that impressed me.
Fullscreen mode has been renamed to Presentation mode, click on that button on UI to switch to presentation mode which earlier called as fullscreen mode, you can exit from Presentation mode at any time by pressing Esc button on keyboard.
You can now use “Open file” control on UI to open any PDF file from your Computer.