If you experience the error message, "Not all signatures are valid" in Adobe Reader, there are some settings you need to have adjusted in Adobe Reader.

It is usually not because the signature generated in Addo Sign is not validated, it is a display issue. Here is a guide on how to get around this. 

1. Open the signed PDF document in Adobe Reader and press CTRL + K, or Edit and then Preferences. 
   
   
2. A pop-up window will appear. Here press Documents. Under the PDF/A View Mode section, select Never. Finally press OK
   
   
3. The signed document will then say Signed and all signatures are valid.