It's very difficult to do something like that in a PDF file (unless it was created using LiveCycle Designer).
You'll be better off editing the original file and then creating a new PDF from it.
Thanks for the query.
As of today, Table editing is not supported in Acrobat Pro DC.
As a workaround, if you do not have access to the the original/source file, you can export the PDF file to Word(.docx), perform editing in Word and then create a PDF back from the docx file.
But, this process is not recommended.
The problem with this is that you lose all the form properties that have been set up. It is like starting from scratch.