Dear support,
We upgraded the api version to 14.9.0 and found that the save to PDF becomes very slow.
FYI, when save in pptx format, it takes around 2 mins, while in PDF format, it requires 20+ mins.
IPresentation ppt = new Presentation(pptTemplate.getInputStream());
ppt.save(reportPath + filename + ".pdf", SaveFormat.Pdf);