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Individual and Composite signature options in Circularo

All Circularo signing methods in Circularo are based on PKI and Electronic Certificates. We offer two distinct signing methods, each utilizing electronic certificates in different ways, as described in this article.

Composite Signature Method (default)

This is the most common method used internationally for business transactions across eSigning platforms.

By default, Circularo uses the Composite signature method for signing documents digitally. This means that the signatures are inserted directly into the content of the PDF document. The entire document is then digitally sealed using the common electronic certificate (either the default one provided by Circularo or one issued on behalf of the end customer).

Should there be more than one signatory in the document, the final signed PDF will be sealed with the certificate of the last person to sign it. This approach is typically simpler and more convenient, as it only requires one electronic certificate.

However, the Composite Signature Method may not provide the same level of security, traceability, and non-repudiation as the Individual Signature Method, as additional information about the signing events is in the Audit Trail / Certificate of Fulfilment, which we provide.

The Composite signature method is recommended for most business use cases especially when the whole signing process is securely managed end-to-end in a controlled environment like Circularo.

Pros of the Composite Signature Method:

  • Signatures are part of the PDF content - Any PDF viewer can recognize and show the signatures correctly

  • Senders can request the signatories to fill in other predefined fields (date, text, checkbox, etc.) during the signing process.

Cons of the Composite Signature Method:

  • Only the last signatory (signing event) in the signing process has their certificate included in the final PDF

  • Timestamp events and signing event details of all participants are included in the Audit Trail (Certificate of Fulfilment) rather than in the signed document itself.

Individual Signature Method

Circularo also supports the Individual signature method, where each signatory digitally signs the document using their own certificate (unless common certificates are used). The signed document contains an embedded electronic certificate for each signing event (signature, initials or stamp). The authenticity and integrity of each signature is therefore apparent from the document itself without any further information needed.

When utilizing this method, each signature is stored in a dedicated signature field within the PDF. These signature fields are not considered a part of the document's content, which means that adding the signatures does not interfere with any previously placed seals.

However, it is important to note that if you choose to use this method, any information other than signatures, initials, or stamps must be included in the document prior to initiating the signing process. Once a signature is added, the content of the document is digitally sealed and any non-signature fields added afterwards would break this seal, rendering the signature invalid.

To incorporate the necessary information, you can either add it before uploading the document to Circularo, or directly within Circularo using annotations in preview before starting the signing process.

The Individual signature method might be the right option if you need to meet particular regulations or adhere to specific policies.

Pros of the Individual Signature Method:

  • Each signing event (stamp, initial, signature) has a corresponding certificate included in the document

  • The information about the signatories and the times when each signing event took place is embedded in the certificate, which is a part of the PDF document itself.

Cons of the Individual Signature Method:

  • Only Signature fields (signature, initials & stamps) can be added to the document during the signing process. Other fillable fields (such as text field, date, checkbox…) become unavailable while using this method.

  • It is a known issue that some PDF viewers (such as Mac Preview) currently cannot recognize and properly show all signatures added to a document using this method due to it being a more advanced, complex approach to eSigning. This issue makes it sometimes impossible to see that a document is signed, which in turn makes it easier to accidentally invalidate the signature.


Though both methods are secure and legally binding, the Composite Signature Method offers a simpler, more convenient approach using a single electronic certificate for the entire document and the Individual Signature Method offers enhanced accountability and stronger non-repudiation by attaching a unique electronic certificate to each signature.

The choice between these methods should be guided by the specific use case, legal requirements, and the desired level of security. It is advisable to consult with legal counsel or a relevant professional to understand the specific implications of using these methods in your particular context.

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