Visual Signature and Digital Signature: What Truly Guarantees Integrity

Visual Signature and Digital Signature: What Truly Guarantees Integrity

In an electronically signed PDF, there are two levels:

• The visual appearance of the signature : the image or the “Signed by…” block visible on the document
• The digital signature : a cryptographic block embedded in the file that software like Adobe Reader/Acrobat can verify

The true guarantee of integrity does not rely on the visual appearance of the signature, but on the digital signature itself. It is this digital signature that confirms the document has not been altered since it was signed and that it was indeed signed by the intended person on the indicated date.

Validation of Signatures in Different PDF Readers

The Preview application on Mac does not allow for the validation of digital electronic signatures.

It may display a signature image (for example, in some documents from DocuSign), but this does not constitute cryptographic validation. Depending on the version used, Preview may also fail to recognize certain digital signatures, such as those used by eZsign.

NOTE: To properly verify the authenticity and integrity of an electronically signed document, it is recommended to use Adobe Reader or Adobe Acrobat.

Why Some PDF Readers Allow Editing of a Signed PDF

Some software, such as built-in PDF viewers (for example, Preview on Mac), do not properly handle digital signatures.

When a signed document is modified and saved in this type of tool:

• The software may completely remove the digital signature
• The PDF may be saved as a new document, without any validation mechanism

Result:

When this file is later opened in Adobe, it is no longer a signed document but a modified copy. Adobe can therefore no longer display a “document modified after signing” warning, since there is no digital signature left to verify.

This behavior is not specific to eZsign. It is possible to create this type of copy from any signed PDF, whether it comes from DocuSign, eZsign, or any other solution, whenever a tool is used that does not preserve the digital signature.

Anyone attempting to alter a copy of a signed document can technically do so. However, only the original version that retains the digital signature remains valid and verifiable.

What this means for the validity and security of your documents

Any signed PDF can be turned into a modified copy using a PDF editor. No solution can prevent the creation of an altered version once the file has been downloaded.

However, what has legal value is:

• The original signed document stored on the platform (eZsign in your case, or on your servers if applicable)
• The validation of the digital signature in a compatible tool such as Adobe Reader or Adobe Acrobat

With eZsign, the original signed document is preserved with its digital signature, timestamp, and a detailed audit trail. Even if a copy is modified, the original remains intact and verifiable.

NOTE: For any authenticity verification, rely on the original stored on the eZsign platform or on validation performed in Adobe Reader/Acrobat.

Conclusion

To ensure the authenticity and integrity of an electronically signed document, it is essential to rely on the digital signature and the original stored on the eZsign / eZmax platform. Even if modified copies may exist, the original remains legally valid , along with its timestamp and audit trail.

Opening the document with a compatible tool, such as Adobe Reader or Acrobat , allows you to verify the status of the signature and confirm that the file has not been altered since it was signed. If in doubt, the original can always be retrieved from eZsign / eZmax to confirm the document’s validity.