Never mind, I sorted it out myself.
To Solve this I had to create a digital certificate and save it. The problem was that Adobe content certificate 10-5 was selected by default .

Hi All, I Just bought your software (PDF-tools) and I am trying to add digital signature in a batch mode. I crated my signature using a png file but when I run the tool I got this error: "Cannot find object or property" followed by the filename. How can I fix it. I also tried adding a sign...