A presentation file (ppt) is in pdf format. We need to edit it. How to get back original ppt formatted file for modifying?
This is much like answering this question: “I have a photo of a building. How can I reconvert it to a real building?”
PDF is absolutely different thing, it’s not the original document, it only looks alike. You can import PDFa to editable formats, but that won’t be the original file, just something needing much work.
You can open the PDF file in LibreOffice Draw. As explained by @mikekaganski, you then no longer have an original PPT file.