Advanced PDF Text Editor

I need a simple, reliable way to edit the text inside existing PDF files without converting them to Word first. The tool—or script—you build should let me:

• Click straight on any line of text within the PDF and fix or replace individual words.
• Insert brand-new sentences or paragraphs anywhere on the page, keeping the flow of the original layout intact.
• Adjust font size, style, and colour so the new or edited text blends seamlessly with what is already there.

Image content can stay exactly as it is; my focus is purely on text manipulation. A clean, uncluttered interface is ideal, but command-line options are acceptable if they speed things up and still give me precise control.

Please deliver the compiled application (or script with clear setup notes), a short usage guide, and a sample edited PDF that proves each of the capabilities above works as described.