Android APP : PDF viewer with highlighter, eraser and electronic signature

I want to make an android app that shows the consent form in pdf and gets the consent. Electronic signatures must be available in the signature space, and text must be entered where the name or number is entered. Additionally, it should also have highlighter and eraser functions. The electronic signature referred to here should be a state in which integrity is guaranteed, not a general image. I know that a free library called iText supports this function. I would appreciate it if you could tell me the period and the estimate amount.