Embedding PPT in the PDF

You can add a link to it like you would to any other web-site, but it won't be "embedded" in the PDF.

To do that you need to drop it into the Attachments panel. Then a script can be used to open it when a button is clicked, or you could simply double-click it from that panel directly.

You can add it to the PDF as an attachment.

Search for "Add attachments to PDFs" on this page: https://helpx.adobe.com/acrobat/using/links-attachments-pdfs.html

Also, you might want to convert this PPT to PDF before attaching it, it will always be lighter.

In any case, be aware that an attachment placed in a PDF is zipped (non-destructive compression), so the weight of the final document will be less than the sum of the PPT + PDF weights.