As far as I can tell there are two ways to automatically ensure the page is large enough to fit a drawing so that the drawing does not go beyond the page boundaries. These are the LayoutOptions.EnlargePage property and the SaveOptions.AutoFitPageToDrawingContent property.
I have tried both and both of them still result in my diagram going beyond page boundaries. However, when I try leaving them out in code and manually clicking the related option in Visio 2016 instead, it works. Therefore it seems to me that these options are not working properly in Aspose.Diagram. I have attached my example code and a picture of the output in Visio 2016. I am using the evaluation version of Aspose.Diagram for .NET v19.3.
asposeExample.zip (31.3 KB)