Sometimes, you set Facing as the default display layout, for example, but when you open a particular PDF, it always opens in Single mode.This type of document usually has author settings.
Things you need to understand:
• If the document has its own page layout setting, a ‘single’ mode for example, this file will always is open in Single mode. The page layout setting is set up by the initial author of this document. To view this, you can use Foxit PhantomPDF. Open the file with PhantomPDF, go to File > Properties > Initial View, where you can see the layout settings for this document.
• In PDF standard, PDF Reader will always adhere to the document initial settings. So when Reader opens a document, it will always check the document initial settings first, if there are any, the documents settings will apply, if none, Reader preferences settings will take effect. You can change the layout setting at the current view by going to VIEW > Page Display > Facing for example.
Since version 9.0, we've added "Override Page Display" settings under File>Preferences>Accessibility so we could force page layout/zoom level as desired.