How do I integrate electronic signatures into existing systems via API?

Electronic signatures are integrated through a web API: your application passes the document or its hash value to the signing service, the signatory authenticates, and the completed signature is returned to the application.

primesign provides a Document Signing API for PDF documents and a Hash Signing API for cases where the document content must not leave your own system boundary. Experience shows the integration effort sits less in the signature itself than in identity binding, error handling and status callbacks.

Here's how an API integration typically runs:

• Settle the architecture: Decide who prepares the document and provides the viewer — the signing service or your application. That choice determines which API you use.
• Define the signature level: Determine which eIDAS level each document type requires and how signatories will be identified.
• Set up a test account: Start with a test account and the API guide. A straightforward signing operation is usually connected within days.
• Submit the signing request: The application passes the document or hash value along with metadata such as signature position, level and signatory reference.
• Embed authentication: The signatory is guided through authentication — via eID, certificate or an existing account — and authorises the request.
• Return and filing: The signed file is returned, filed against the system of record, and the operation is logged.

What actually drives integration effort:

• Identity binding: How signatories are identified and authenticated is more involved than the signing call itself.
• Error and status handling: Abandonment, timeouts and resumption must be modelled properly so processes do not stall.
• Number of providers: For software vendors the provider count is the real cost driver — a QES is recognised EU-wide under Article 25(3) eIDAS, so one listed provider suffices.

primesign provides a Document Signing API, a Hash Signing API and a dedicated Cash Box API for RKSV receipts, complemented by ready-made connections to applications such as Adobe Acrobat Sign and Fabasoft. Through OEM and reseller models, integrators can serve every EU market from a single integration.