I read that changing paragraph's text, removes all styles and runs from it! so, this is not an option for me, since I need to keep them for my new document. The other approach I tried was using runs ...

This tool searches and replaces text in PDF files using PyPDF. Some alternative approaches are discussed here and here. Needs pypdf 5. pypdf 4.x.x will not suffice. This tool is known to work with ...