Specifies page rotation, in degrees. Used for routines that set/get the value of a page's Rotate key.
Values:
| IG_PDF_ROTATE_0 | Zero rotate angle. |
| IG_PDF_ROTATE_90 | Rotate angle is 90 degrees. |
| IG_PDF_ROTATE_180 | Rotate angle is 180 degrees. |
| IG_PDF_ROTATE_270 | Rotate angle is 270 degrees. |