I cannot give access, due to sensitive data of my subscribers (there are strict Laws here in Italy about Privacy). I need a different solution.
I tried to deactivate all other WP plugins, but PDF Stampers doesn’t work also in that case.
Settings are OK: I choose BLACK text and it should be applied to white background of PDF… I also tried to add Images watermark, but also this option is not working. There aren’t other settings for your plugin, it has quite simple settings, but it doesn’t work for me.