Word processor like "editing" is not tolerated by PDF (the file format/technology discussed and described by the ISO Standard for PDF, ISO 32000-1). Minor touchups are tolerated. The textual characters have to be renderable text (a scanner's output image of text is a picture of text not "real" text).
Open the PDF with Acrobat XI.
Click-path:
Tools - Content Editing - Edit Text & Images
Be well...