What it is for: open a PDF, add text, notes, drawings, shapes, images, a signature or today's date, move and resize items precisely, reorder or delete pages, and download the edited PDF. It is free to use.
To change words already in the PDF, use Edit Text: drag a box over the old words, then type the new words in the box that opens. This covers the old words with white and puts your new words on top. It does not delete the old words from the file underneath, so do not use it for sensitive information that must be removed.
Your file stays in your browser. Nothing is uploaded to a server. The PDF is opened, edited and saved on your own device.