If you scan a form you get a picture of the form - not an editable document. To convert it to editable text you need some Optical Character Recognition (OCR) software. Even then, the OCR will have to guess what the layout is - ie spaces between letters can be spaces, tabs, carriage returns etc.
It might be just as easy to write the blank form from scratch. Then open it, add your words and save as a different name, or save the blank as a template (they've got a .dot extension - its an option below the line in which you enter the filename when saving)
If the form has to look exactly like a photocopy of the original, scan it and fill it in by adding wording in text boxes, which you can format to have no border lines.