Thank you for writing.
RadPdfViewerNavigator is basically RadCommandBar
control, so using the latter's API you can access the buttons and change their images. Here is an example:
radPdfViewerNavigator1.Rows.Strips.Items.Image = myImage;
On the question how to load pdf in RadPdfViewer, please consider the following article: http://www.telerik.com/help/winforms/pdfviewer-getting-started.html
I hope that you find this information useful.
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