Hi Shubhi,
Thank you for contacting support. Please note, the page size of the source Visio and page size of the new diagram are not same. However, we can manage zoom level by setting the drawing scale property before saving the resultant PDF as follows:
[Java]
newDiagram.getPages().getPage(“newpage”).getPageSheet().getPageProps().getDrawingScale().setValue(1.23);
newDiagram.save(“E:\Practice\asposeprac\asposeDiagram\ShapeOutput.pdf”, SaveFileFormat.PDF);
Please let us know in case of any ambiguity or questions.