prevent the saving of signatures

We would like to prevent the saving of signatures within Acrobat Reader.
The function fill and sign PDF forms can save a signature or initials - 
we want to prevent this possibility by configuration. 
The possibility of setting a check there should be prevented directly.

Our customers sign the PDF with the fill&sign function and we want to prevent,
a signature from being saved as an error.

I checked all the settings but couldn't find a way.

Thanks in advance for your help