Converting scanned form documents to text requires good OCR software and a
lot of patience.
An alternative would be to build a table over the image inserted behind
text, again a lot of work and hardly practical for a one-off, unless you
have far too much time on your hands.
If you have a lot of similar forms to fill then you need an application
designed with that it mind. Abbyy used to include a form builder with its
Finereader OCR software but now appears to sell it as a separate
application. My guess is that this would be far too expensive for casual
use.
You could always use a pen. Sometimes old technology is the best option.
Computers are only the better option if they save you time. On this occasion
that is most unlikely.