Thank you for inquiring Aspose.Slides.
I have observed your requirements and worked with the presentation file shared by you. I would like to share that the pptx file contains text which is white in color, and a Custom Combination chart. If you convert to PDF after changing the text color then you will notice the text is there however the chart is lost, which is an issue. A ticket with ID SLIDESJAVA-34810 has been logged in our issue tracking system to further investigate and resolve the issue.This thread has been linked with the issue so that you may be automatically notified once the issue will be resolved.
I am attaching the generated output pdf file which has text on it for your kind reference.
We are sorry for your inconvenience,