Multiple signatures and identifiable elements to ensure a valid document

I have multiple signatures on a document that I created in Acrobat DC. The users applying the signatures are using Reader. After the forms have been filled in and the signatures applied, I am seeing different messages for each document saved in the blue bar: ‘Signed and all signatures are valid. Document was updated after signing. Open Signature Panel to view the document change history. Please fil out the following form’ – The green check is there but if the message is saying ‘document was updated after signing’, is it invalid? ‘Signatures are valid. Please fill out the following form’ – That looks valid to me. ‘Signed and all signatures are valid, but with unsigned changes after the last signature. Please fill out the following form’ - That message has the yellow! That’s not valid, I get that When looking at the Signature field panel, I see ‘Form Fields Filled In’. It does NOT show an error message if the second person signing has modified it before signing it, even if another signature has been applied. It DOES show the yellow! symbol if the person signed it and then made changes. This is when I see the message in the blue box ‘Document was updated after signing’ I NEED TO KNOW WHAT IDENTIFIABLE ELEMENTS I SHOULD BE LOOKING FOR TO ENSURE THE DOCUMENT IS VALID I have added the digital signatures by going Prepare Form – Digital Signature and adding a box for the digital signature to be applied. On the Digital Signature Properties field the options to pick are: 1.‘Nothing happens when signed’ 2.‘Mark as read-only:’ - ‘All fields except these’ and pick the next signature field. Option 1 - if ‘Nothing happens when signed’ is picked it will allow the next person adding the second signature to make modifications, but will this make the signatures invalid? I should mention, I didn’t set up the digital signatures this way, they were set up by another person. Option 2 - should I set up the digital signatures by choosing ‘Mark as read-only’ on my document to ensure the document is valid?