Questions about PDF Signatures

Hi - I am working on a fillable form for my business. Had two questions...

1.  I noticed that the person filling in the form can “clear” their digital ID signature by right clicking the signature and selecting “clear”. Do you know of any way to prohibit that? 
2. Once I sign one note and then make changes to the document by writing in another note, the first signature becomes “invalid” because “there have been changes made to this document that invalidate the signature." Is there a way to prevent that from happening? For these pages, the user will be signing the page after each entry - two enttries per page. They will then go back in and add another note in the same document, when needed.

Help much appreciated. Thanks!