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Click the up arrow button (highlighted in the blue square) to hide the webview WebView toolbar.
This will enable the PDF viewing options to be accessed.
The PDF viewing options are displayed at the top of the page as shown below. The button on the far left enables the thumbnails view to toggled on and off. The button to the right of scaling button enables auto scaling to fit the page to the height or the width of the WebView. It is also recommended to adjust the width of the WebView (using Edit mode) so that the aspect ratio of the layer matches closely with the aspect ratio of the PDF page. Finally, the Present option in the menu on the far right, gives a view of the page which fills the WebView layer and hides all thumbnails and menus.
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