...
Adding files to an existing PDF File.
PDF Portfolio
In this mode Acrobat creates a PDF container that includes files in their original format. Thus, a .pptx file is still editable (and probably extractable) as .pptx. When viewed in Acrobat Reader, these files are still in their original format. This could cause complications for less patient readers, since A-Reader does not automatically preview these files. Adobe purports to include web pages, but in my test it handled https://www.canisius.edu/academics/office-academic-affairs/academic-institutes-and-centers/center-online-learning-innovation poorly.
Adding Page Numbers to a PDF
...