Hi Imran,
I appreciate your patience in this matter. I was able to reproduce this issue you’re seeing - after investigation, I found a system property specific to PDFNet that you can set to accomplish your intended use case without altering the java.io.tempdir. This system property is called com.pdftron.systemloadtmpdir and can be used in the same way as java.io.tmpdir.
I created an extended forum FAQ post regarding this topic with more details that you can find here. Please take a look and let me know if you have any additional questions!
Thank you,
Kaden Rettig
Associate Technical Support Engineer
Apryse Support Team