Why there is a patch
When the old words cannot be removed cleanly, we cover them with a block the colour of the page and write the new words on top. On white paper it is invisible. On a photo, a colour fade or a tinted row, no single colour matches, so it can show. Likely cases are marked Overlay only before you type.
Make it less noticeable
- Keep the new words about as long as the old ones.
- Change the whole line, so the patch follows a natural edge.
- Open the downloaded copy at normal size before sending it on.
A patch hides nothing
The old words may still be in the file. Do not use editing to remove confidential information. Why editing is not redaction.
Related: why the text will not change, edit the text in a PDF.