What do you mean by editable? Is the document a scan or does it have text that was created as a PDF from the original file.
If it is a scan, you need to run OCR (probably clear scan) to get text that you can edit. The problem is that OCR is generally not perfect and you need to review the entire document to be sure it is correct.
If it is text, then you might be better off saving it as a WORD document and fixing any problems there, then create a new PDF. Getting a good WORD file is not always easy, but editing in Acrobat should only be used for very minor edits.