Can you please provide me with code snippet for converting pptx to pps/ppsx document?
I have observed your requirements and like to share that Aspose.Slides can save a presentation file to PPS and PPSX file formats. Actually, we have SaveFormat Enumeration, that you use to give the save format while saving the presentation. When you set SaveFrmat.Ppsx or Pps while saving the presentation, it will be saved in respective file format.
Aspose.Slides also supports adding audio and video frames inside presentation file. Please visit this documentation section for your kind reference in this regard. Please share, if I may help you further in this regard.