Glossary
What is a tamper evident?
Tamper evidentent is tamper evident when any change made after signing is detectable. A digital signature gives this property: alter one byte and verification fails.
Tamper evident is not the same as tamper proof. Someone can still change a file. What they cannot do is change it and keep the signature valid.
This is why a signed loan PDF is useful in a dispute: either the signature verifies, so the file is the one that was signed, or it does not.