How much does it cost to integrate e-signatures?

What drives the cost of embedding e-signatures in your software, the costs teams forget, and a method to estimate yours from volumes, signers and languages.

Published Oct 3, 2026 · 8 min read

There is no single price for integrating electronic signatures into software. The total cost depends on a handful of variables you already know: documents sent per month, signers per document, languages, the signature level you need and the countries where you sell. This guide lists the cost drivers to quote, the costs teams discover too late, and a method to build your own estimate without invented figures.

It is written for software vendors adding PDF signing to their product: an HRIS sending employment contracts, a CRM sending quotes, a customer portal collecting mandates, or property software handling leases.

The cost drivers to plan for

Integration cost splits into an initial investment (your team's work to connect signing) and recurring costs (usage, trust, storage, maintenance). Use the table below as a checklist for vendor conversations and internal estimates.

The first line is the one most often underestimated. A demo flow connects quickly. A flow that handles reminders, cancellations, network errors, multiple signers and statuses shown to your customers takes more time.

Comparing pricing models

Established providers such as DocuSign, Adobe Acrobat Sign or Yousign each publish their own terms. The most useful comparison is how each model behaves with your real usage.

For a software vendor, per-user pricing rarely fits when your customers and their own teams send the documents. A model tied to volume or scope follows the growth of your customer base more closely.

The costs teams forget

These items rarely appear in a first estimate. They still weigh on the budget as soon as volume grows.

• Failed or cancelled requests: a contract resent after a data entry error, a quote replaced by a new version. Depending on the model, each one may consume a unit.
• Reminders: every nudge to a signer costs support time and sometimes a billed email or SMS.
• Evidence archiving: the signed PDF is not always enough. The evidence report and activity log must be kept as long as the document.
• Duplicates: without an idempotency key, a request retried after a network failure can create two requests.
• Re-integration when changing provider: new API calls, new webhooks, archive migration and a full retest of every flow.

Estimating the cost for your product

A useful estimate starts from your real usage. Gather this information before any commercial discussion:

1. Monthly volume of documents sent, today and in a year.
2. Average number of signers per document (an employee and an HR manager, a customer and a sales rep).
3. Languages of the signer journey: Arabic, French, English, or several in the same document.
4. The signature level you need and how signers are identified, which determine the certificate and identity verification.
5. The countries where your customers sign, which guide the choice of trust service provider and retention rules.
6. The retention period your customers require for signed documents and evidence.
7. The number of integrations to build: one application, or several products in your range.

Worked example with variables

Take an HRIS that sends employment contracts for signature. Describe the cost with variables. You then replace each variable with your own figures and with the terms you receive from each provider.

D  = documents sent per month
S  = average signers per document
r  = average reminders per signer
a  = share of requests cancelled or redone (between 0 and 1)
v  = share of signers with identity verification (between 0 and 1)

Billable units
  per envelope    = D × (1 + a)
  per signature   = D × S × (1 + a)

Recurring volume
  verifications   = D × S × v
  reminders       = D × S × r
  storage         = D × average size × retention period

Initial cost
  = integration days + security review + multilingual work

Monthly estimation model (fill in with your data)

For this HRIS, S equals 2 (the employee and the HR manager). If the same product later adds an amendment signed by three people, S increases and per-signature pricing reacts more strongly than per-envelope pricing. If your customers require identity verification for every employee, v moves close to 1 and that line becomes significant.

Run the calculation for your current volume and for your volume in a year. The best-fitting pricing model is the one that stays predictable in both cases.

How pricing works with Khatm

Khatm has no public price list. Cost depends on the scope of your project: the application to integrate, volumes, languages, the connections required (identity provider, PKI, HSM or trust service provider) and the signature level. A proposal is prepared after scoping.

You do not need to wait for that proposal to make progress. The API sandbox is self-serve: create an account, generate a test key and build your integration. That lets you measure the first line of the table, development time, with your own code. Read the API documentation

• The client_reference field makes request creation idempotent, which prevents duplicates.
• Reminder and cancellation endpoints are available in the sandbox, so you can test the cases that cost the most.
• Each request accepts up to 10 signers and 100 fields, with a PDF of up to 8 MiB.
• The signed PDF, the PDF evidence report and the JSON evidence are retrieved through the API.
• The signer journey is available in Arabic (right-to-left), French and English.

Going to production is prepared with Khatm as part of the implementation: adapting the flow and your brand, integrating with your developers, connecting signer identity and the certificate from your PKI, HSM or trust service provider, RFC 3161 timestamps when that provider supplies them, and a guided rollout. Khatm is not a qualified trust service provider and does not issue certificates, so that cost depends on the provider you choose. See the implementation offer

Where to start

1. Try the public demo to see a really signed PDF, without an account.
2. Get a sandbox key and connect a first flow in your product.
3. Read the docs to estimate the remaining work on reminders, webhooks and evidence.
4. Fill in the estimation model above, then prepare production with Khatm.

PDF signing built into your software, under your brand, in Arabic, French and English. Test in the sandbox; we guide you all the way to production. Try the demo Get a sandbox key Prepare production

General information, not legal advice. Confirm the requirements for your transaction with the appropriate adviser or receiving authority.