Thank you for your advice, it's may be an easier task to make small changes of text in pdf files. And for large change to text within pdf file, if I have the orginal document, it's really straight method to edit in it and make a new pdf file.
But I am wondering, if I receive a plain pdf form and I want to fill out it on screen rather than by hand. What can I use? Probabaly Touchup text tool is the right choice.
Please don't suggest the pdf converter to me, I have used many of them that the formatting is tend to be wrecked after conversion. And Converting to text is likely to lose layout and image.
If you recieve a form it will usually have form fields into which you can just type text (or make selections). If the creator of the form enable it, then you can even save the form, or just print or submit it electronically.
IIf the file has no form fields, and it's not locked, then you can add them yourself.