How to find margin of PDF file

We are unable to find the margin of PDF file.
Aspose always return us dimension as
72.0 (top and bottom)
90.0 (left and right)
Through Aspose (v-19.1) we are unable to change the margin of the existing PDF file.

Is there any way we can do so?
We don’t find any Aspose pdf library which can assist us.

Thanks

@helloworld123

Would you kindly share your sample PDF document with us so that we can assist you accordingly after testing the scenario in our environment.