Hello ZoNi,
Please take a look at the
Redaction tool we offer in the Viewer's successor - the PDF XChange Editor:
https://www.pdf-xchange.com/product ... nge-editor
Using that tool you can remove the text permanently (so that it can not be recovered later by any means), and either leave a rectangle that is obvious (e.g. red/yellow) to indicate that there was text that is now gone, or make it the same colour as the background - so that it disappears.
It can not be "blurred" as per your example though, and while hard I can still read the text in the blurred area above
Regards,
Stefan