Collect supporting documents during signing with eSignature API

Sign, track, and store contracts — without the complexity of CLM.

Ask for the file when you ask for the signature, with the Signeasy eSign API.

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Karthikeyan KC

Updated on

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3

min read

Published on

July 31, 2026

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3

min read

Karthikeyan KC

July 31, 2026

•

3

min read

Collect supporting documents during signing with eSignature API

Key Takeaways

Collect supporting documents from signers as part of the signing experience using the Signeasy eSignature API.
Request different documents from different recipients within the same envelope.
Mark attachments as required or optional to match your business workflow.
Keep signed agreements and supporting documents together in a single transaction.
Trigger automated workflows using webhooks when attachments are uploaded.
Download signer-uploaded files alongside the signed document and signature certificate using the existing API endpoint.

Electronic signatures are only one part of many business workflows. HR teams need identity documents, procurement teams need W-9s, and contractors often need to upload supporting specifications before a contract is complete.

Without built-in document collection, these files are usually exchanged later over email, creating delays and manual follow-up.

Signer Attachments lets you request those documents during signing, so signatures and supporting files stay together in the same transaction. Now, this feature is live on the Signeasy eSign API.

Whether you're onboarding employees, collecting vendor paperwork, or managing project documentation, you can now capture everything you need in a single signing experience using the Signeasy eSignature API.

Why collect supporting documents during signing?

Asking someone to sign a document and then email supporting files afterward creates unnecessary friction.

Someone has to remember to follow up. The signer has to find the documents later. Files arrive in separate email threads, often days after the contract has been signed. Someone on your team then has to match those files back to the correct transaction.

Signer Attachments eliminates those extra steps by making document upload part of the signing flow. Signers upload the requested files before completing the agreement, so everything is collected together and stored with the completed envelope.

Common use cases of requesting documents along with signature requests

Signer Attachments can be used anywhere signatures and supporting documents need to be collected together.

Employee onboarding: Request a driver's license, passport, or work authorization documents alongside an offer letter.
Vendor onboarding: Collect W-9s, insurance certificates, or compliance documents with supplier agreements.
Construction and engineering: Ask contractors to upload blueprints, drawings, or specification sheets before signing a statement of work.
Financial services: Collect identity documents or supporting paperwork required for compliance.

How Signer Attachments work in Signeasy's eSign API

When you create or send an envelope, include an attachments array in your request.

Each attachment request is associated with a specific recipient and lets you:

request one or more files
provide instructions for the signer
assign a label to each requested document
mark each file as required or optional

Different recipients can be asked to upload different documents within the same envelope. In the below example, the first recipient is asked to upload a driver's license and may optionally upload a passport, while the second recipient is required to upload a blueprint before completing the signing process.

It’s just an extra step on the same create or send an envelope endpoint, as an additional attachments array alongside your recipients:

{
  "attachments": [
    {
      "recipient_id": 1,
      "message": "Please attach the requested proofs.",
      "files": [
        {
          "label": "Driver License",
          "required": true
        },
        {
          "label": "Passport",
          "required": false
        }
      ]
    },
    {
      "recipient_id": 2,
      "message": "Kindly attach the blueprint.",
      "files": [
        {
          "label": "Blueprint",
          "required": true
        }
      ]
    }
  ]
}

Require attachments before signing is complete

If a file is marked as required (required: true), the signer must upload it before they can complete the signing session.

Optional attachments allow signers to provide additional documents without blocking completion.

This gives you the flexibility to collect only the documents that are essential for your workflow while making supplemental files optional.

Automate workflows with webhooks

If you're already using Signeasy webhooks, Signer Attachments fits into your existing integrations.

Webhook events indicate whether the requested attachments have been uploaded, allowing your application to trigger downstream workflows automatically.

For example, you can:

start an employee verification process after identity documents are received
route agreements for internal approval only after all required files are uploaded
synchronize supporting documents with your document management system
notify internal teams when a transaction is complete

Download signer-uploaded documents

Once uploaded, you can pull the files back through the API instead of asking the recipient to email them to you separately.

Use the existing download a signed envelope endpoint and include the include_attachments=true query parameter to download:

the signed document
the signature certificate
all documents uploaded by signers

Because everything is tied to the same envelope, there's no need to reconcile files received through separate email conversations.

Available on the Signeasy API Advanced Plan

Signer Attachments is available on the Signeasy API Advanced Plan.

If you're already on a different plan, contact your account manager or email api-support@signeasy.com to enable the feature.

If you're evaluating the Signeasy eSignature API and would like to see how Signer Attachments fits into your workflow, we'd be happy to help.

Frequently asked questions

How do I request a file from a signer through the API?

Add an attachments array to the same create or send envelope request you're already using. Each entry names a recipient_id, a message telling them what you need, and a files list with a label for each file. You don't need a separate endpoint or a follow-up call.

Can I request more than one file from the same recipient?

Yes. You can request one or more files from a signer by defining multiple items in the files array. Each requested file can have its own label and requirement setting.

Can I make some attachments optional and others required?

Yes. Set required to true on any file object and the recipient can't complete signing until they've uploaded it. Set it to false and it stays a nice-to-have, so you can mix mandatory and optional documents in the same request.

How do I download the files a signer attached?

Use the same download a signed envelope endpoint you already use for the completed document and its certificate, and add the include_attachments parameter set to true in the URL. The signer's files come back alongside the signed document itself, no separate email thread required.

Can different recipients on the same envelope be asked for different files?

Yes. The attachments array takes one entry per recipient_id, so recipient one can be asked for a driver's license and a passport while recipient two is asked for a blueprint, all within the same envelope and the same request.

Can I automate workflows after attachments are uploaded?

Yes. If you're using Signeasy webhooks, you can detect when attachments have been uploaded and trigger downstream workflows such as identity verification, document review, approval routing, or syncing files with your internal systems.

Karthikeyan KC

He is a Product Manager at Signeasy, passionate about discovering and solving problems related to eSignature API, developer experience, digital trust, and security. His work focuses on aiding businesses of all sizes in adopting digital transformation and efficiently implementing paperless transaction workflows.