You can get the dimensions in the inches from the documentation. Just open the PaperSizeType.html as shown in the screenshot. You can find offline documentation in any latest release e.g. Aspose.Cells for Java 16.12.0,
We need more clarification of your requirements. I have attached the sample excel file. Please take a look on it and tell us what values do you want to get out of it. This will help us understand your requirements closely and precisely. Thanks for your cooperation in this regard and have a good day.
We have logged your requirement in our database as a New Feature request. We will look into it and implement it if possible. Once, there is some fix or other news for you, we will let you know asap.
This issue has been logged as
CELLSJAVA-42132 - GetPaperWidth and GetPaperHeight methods needed in PageSetup