Which is the sanctioned way to retrieve the page-level orientation angle?

By now, I have become familiar with the fact that each Path has its own transform matrix.

However, I noticed that my application displays some page rotated. Acrobat shows them in landscape and my app in portrait. I used a CosLevel navigator and discovered the following page-level variable:

    trailer/Root/Pages/Kids/0/Rotate

whose value is typically 0, 90 or 270.

I could resort to Cos and retrieve it but I suspect that is not the Best Practice.

How should I retrieve it?

TIA