Mateusz Pniewski

CEO @ TransactionLink

Top 18 e-Signature APIs to Use for Digital Onboarding

Finding an e-signature API that works with your existing workflow can be cumbersome so we’ve put together a list of the top 18 APIs that we like working with.

E-signature APIs are paramount to many different industries, from banking to ecommerce and everything in between. In order to make your digital onboarding seamless your customers need to be able to sign documents electronically and in real-time, or you could lose their business. Finding an e-signature API that works with your existing workflow can be cumbersome so we’ve put together a list of the top 18 APIs that we like working with.

With TransactionLink you can integrate many different e-signature APIs into your digital onboarding flow, along with many other APIs tools, leading to better online conversions. 

What is E-Signature Software?

E-signature software allows you to receive, sign, and send documents digitally, instead of physically. Whether you're a global ecommerce business or a local legal firm, sending contracts and other documents to clients for signatures digitally is much quicker and easier than the alternatives. Businesses that utilise e-signing software make processes simpler, leading to happier customers.

Best e-Signature APIs for Digital Onboarding

1. is a web API platform maintained by ByteScount. They provide a PDF form filler API which enables organisations to fill interactive PDF forms, fill out fields using field names mapping, manage PDF e-signatures, create ‘flattened’ (read-only) PDFs while also supporting integrations with more than 300 business automation solutions including Zapier, Make, Airtable, Salesforce and Google Apps Script. API supports C#, PHP, Javascript, .NET, ASP.NET, Java, Visual Basic, and more.

While is definitely heavily developer focused, teams with the ability to implement their features will benefit from a robust all-in-one PDF management system, including e-signature, for digital onboarding. What’s more is their highly rated support is developer lead, so you can expect to receive highly effective support to ensure that technical implementation goes as smoothly as possible. 

2. Rocket Sign

Making sure onboarding documentation is legally watertight is, of course, a huge concern for any business. Addressing that need directly is the primary focus for Rocket Sign, the legal signature API developed by Rocket Lawyer - an online legal technology company helping businesses and individuals make legal documents and get attorney advice.

A key USP for Rocket Sign is that it offers users access to a lawyer for legal advice relating to their documents. Perfect for start up businesses who may not yet have access to in-house legal counsel. 

Uploading and sharing documents for e-signing is a cinch with Rocket Sign’s user friendly platform. For full customisation of the digital onboarding experience for your customers, the Rocket Sign API is provided for free, promising simple integration along with a mobile first, feature rich, scalable and secure e-signature solution. 

3. Signable

Signable provides an e-signing API with a strong emphasis on a simplified user experience. Their dashboard makes it easy to create documents from scratch for signing, or to upload existing Word, Excel or PDF documents to send and sign. 

The REST based Signable API enables full integration with your own website or CRM system - perfect for implementing a truly scalable and custom digital onboarding solution for your business. 

An added bonus to Signable’s offering is the ability to make use of Webhooks, which are used to get an instant response to an action performed within Signable (for example when a customer opens that sales contract you’ve sent them).

4. Dropbox Sign

In 2019, Dropbox acquired e-signature startup Hello Sign, launching the established file sharing platform into the e-signature game. 

Given their existing credentials and market share in digital file management, the acquisition propelled Docusign into direct competition with DocuSign and Adobe with the newly labelled offering: Dropbox Sign.

With a high reliability factor in terms of service and security, Dropbox Sign also places a heavy focus on a simplified user experience and awesome integrations. 

Strong pre-baked integration capabilities with Hubspot CRM, Salesforce, Oracle, Active Campaign (among many others) demonstrate the suitability for Dropbox Sign to be an ideal customer onboarding solution for any business.

A powerful API allows for custom integrations that are fast to implement. While a free sandbox is available to play with and test the Dropbox Sign API, putting it into practice will require a premium subscription.

5. PandaDoc

PandaDoc is a cloud based document management service which aims to make creating, managing and e-signing documents as easy as possible. Geared towards collaboration within document workflows, PandaDoc makes an excellent choice for a digital onboarding experience.

It also offers real-time oversight of documents so you can keep track of approvals, comments, document versions and, of course, when those all-important documents have been signed. 

PandaDoc’s ease of use makes it a tool of choice for non-technical stakeholders. It has many out-of-the-box integrations available for leading CRM platforms, including Salesforce and Hubspot. With the PandaDoc API for electronic signatures you can build custom CRM integrations, making online conversions flawless.

6. signNow

SignNow is the e-signature brand of AirSlate - a cloud based all in one solution for automated document workflows. AirSlate acquired SignNow to seamlessly integrate with their existing automation solutions to provide a holistic one-stop shop for workflows that require e-signatures, including digital customer onboarding processes. Using the SignNow API you can achieve full brand customisation of your documents, and make use of a library of template documents with fillable fields to help scale your digital onboarding experience. 

SignNow allows you to sign and send documents for signing from automated workflows all within one digital ecosystem. The SignNow dashboard enables document managers to create automations, assign roles within documents, add notifications, and integrate with CRMs and databases without needing any code. 

SignNow is noted by users for its ease of use on both desktop and mobile devices - an important factor for any business within their digital onboarding experience. 

7. Foxit PDF Editor

Foxit has been a household name in the PDF business for decades. The software company continues to be a global leader in PDF standards and tools. Its all-in-one PDF SDK solution for PDF management allows you to create, edit and sign PDF documents quickly and easily. 

Given Foxit PDF Editor’s focus on creating a simplified PDF editing user experience across all devices, it is certainly worth considering as a solution for your digital onboarding needs. This focus on a simplified user experience has been noted as a strong point for the tool among its user base.

The Foxit PDF SDK is trusted by some of the world’s largest companies so would be a very good match for those looking to create highly customised, scalable e-signature workflows. What’s more, Foxit’s SDK sales team are PDF experts and coders by trade who will assist you throughout your proof of concept process. So expert advice is always available.


8. Adobe Acrobat

Adobe’s Acrobat software has the benefit of familiarity among consumers as it is a long established desktop client for PDF management used by individuals and organisations alike. Currently over five million businesses trust Acrobat to create, edit, convert, share and sign PDF documents. You can create customised integrations for your own organisation’s onboarding experience using the Adobe Sign API.

Even as a household name among desktop clients for many years, Acrobat has kept up with the need for cloud based, mobile document management and should provide a robust solution for digital onboarding workflows which require e-signature capabilities. 

Users of Adobe Acrobat appreciate the efficiency of editing forms, which, combined with its accessible and straightforward user interface, bodes well for a frictionless customer experience.

9. Eversign

Eversign is an e-signing solution that was recently acquired by PDFTron - a technology platform that brings PDF, CAD, and MS Office capabilities to any software with a powerful API that is trusted by some of the world’s biggest companies. With its parent company’s credentials, eversign itself offers a fully-fledged REST API to create workflow automations and design a dream, customised, digital onboarding experience. 

Eversign provides a secure, easy to use and scalable e-signature solution for businesses of all sizes - from individual freelancers all the way up to large organisations. 

While some users in the past have noted the free tier of Eversign to be a little limited, it should be worth exploring the merits of a premium subscription as the tool has an excellent reputation for its usability and its collaborative document management. 

Custom technical integrations are possible with the Eversign API. Given the recent acquisition by PDFTron, this should demonstrate the reliability of Eversign’s custom integrations and the ability for the API SDK to continue innovating into the future.

10. SignRequest

SignRequest allows you to turn any PDF, Word or Excel file into an e-signable document. It’s intuitive dashboard enables organisations to segment their teams to create efficiencies in document workflows. 

SignRequest also allows for custom branding to be added to the entire document lifecycle. So if it is your choice for your digital onboarding e-signature solution, you can be sure that your customers will have the opportunity to enjoy an on-brand experience. Native integrations include with Salesforce, Google Apps, Slack (among others).

Perhaps an indication of the growing demand for e-signature solutions to digitise business workflows, SignRequest is yet another example of an e-signature startup in the midst of an acquisition having been taken over by in early 2021, strengthening the credence of the SignRequest API and perhaps demonstrating the future potential for more native integration capabilities.

11. DocuSign

DocuSign is a sure bet to be front of mind for most people when they need an e-signature solution. As a long established, global leader in the space, DocuSign enjoys the trust of more than a million customers and a billion users.

DocuSign allows users to centralise contracts and agreements on the cloud and provides crystal clear oversight on the progress of interactions with documents that have been sent to a client for e-signing. While the more basic functions of the platform are quite intuitive, it has been noted amongst users that some training or onboarding may be required in order to make full use of the array of document management features offered by DocuSign.

Custom integrations with robust security through the DocuSign e-signing API and over 400 integrations available makes DocuSign a very attractive option for businesses of all sizes looking to transform their digital onboarding experience.

12. Lightico

Lightico is on a mission to simplify complex customer processes and to help businesses and customers alike get things done. Its e-signature solution is designed to be mobile friendly, making the onboarding experience that much easier. It is set up to remove friction for customers and provide tidy, seamless integrations for the organisations and has received high praise for the efficiencies it creates within these workflows. 

A strong focus on ease of use and integrations are intended to allow customers to complete their digital journey, including onboarding, without having to exit the journey, saving organisations time and resources. No code workflows can be utilised to help streamline the entire customer journey, thereby removing barriers to getting the signature. 

Lightico offers global security compliance, out of the box integrations and a powerful API for custom integrations.

13. Box

Have you heard of You may not have but they are used by big brands such as Morgan Stanley, Intuit, and many US government departments. Why do we mention this? Well because, in 2021, acquired SignRequest to branch into the e-signing API market. 

Known for their secure and seamless collaboration solutions, their e-signature solution is all this and more. The Box Sign API and SDKs make integrating their product with other tools easy.

Key features found on their website include signer authentication and tamper-proofing controls, reusable templates, auditing and webflow automation, batch send, and compliance with HIPAA, SOC, ISO, and FedRAMP.

If you are interested in what users are saying about them, you would be pleased to know that users like their security, collaboration and integration features.

14. GetAccept

GetAccept is first and foremost a sales tool to help companies increase revenue, but don’t let that fool you. If you are looking for a good e-signature API tool to slot into your customer onboarding this could be the right one. 

GetAccept calls out their product as fast, scalable, secure, and integrated, making it perfect for setting up all types of signing flows. They have a useful custom signing order feature that further decreases manual processes, and users note the tool to be user friendly.

Does all this interest you? If so, then you should know that GetAccept follows ESIGN, UETA, eIDAS standards, and all communication is done over secure HTTPS connection. Even within their API these standards are easy to integrate. If you are looking for more security you can use their feature to request customers to upload ID verification for extra security.

15. Formstack Sign

Formstack as a business has always been great at helping customers to automate workflows. As increasing efficiency is their goal, they introduced Formstack Sign as a standalone web and API for electronic signatures. 

Yes you get the regular features like audit trails, customisation, and templates that comes with an e-signing API. But you also get much more. They provide single sign-on, custom data retention, and custom Geographical Data centres. These last two features are a must if you have clients in both the US and Europe.

Users have noted that the product is easy to use, and their document upload feature helps reduce customer frustration by being able to send one email with more than one document included for signing.

As mentioned before Formstack is more than just an e-signature product and you can integrate all parts of their product quite easily into your customer onboarding flow using the API.

16. DottedSign

DottedSign makes the process of automating document delivery simple in an era of remote work. When looking for a e-Signature API to help with signing quotes, POs, contracts and much more, DottedSign can provide it all. Their tagline is “Accelerate your revenue growth with a faster turnaround time, and a simple signing flow” and this is exactly what you can do with their product.

DottedSign has good ratings for ease of use for their tool. It comes with all the regular features that you would expect; templates, custom branding, import contacts, encryption, audit trail, and bulk send. Their task management tool is practical and uncomplicated.

A benefit of DottedSign is the ability to use the product with web, Android and iOs devices, which is very important today.

17. CocoSign

CocoSign is an amazingly simple and light API to quickly send, track, and gather e-Signature for customers and clients. Whether you need documents signed in person or virtually you can rest assured that everything will be legally binding and secure.

Their real-time tracking, templates, reminders, and more, shows that this tool is here to help you save time, and maximise efficiency with document management. Other features that differentiate them from competition include URL customisation and custom branding.

For businesses looking for high quality performance and reliability, CocoSign is the solution for you. What’s more, they are the ideal partner for startups and smaller businesses who are looking to scale in the future.

The signatures and personal data collected are protected with SSL encryption, a global standard. And CocoSign reduces human error by processing and proofreading documents online.

18. Legalesign

Based out of the UK, Legalesign works with many big brands across the world to manage millions of signatures within documents. Their legal signature API is suitable for use in organisations of all shapes and sizes.

With knowledge of any language with a https library, Legalesign’s RESTful API gives online access to all functions within its product. Whether you are looking for one function or all them, you don’t need to continue visiting the website to access everything.

If you’re looking for a company that values its customers, Legalesign is recommended for their attention to customer support. Coupled with their high regard for document security, this business has their customers' needs at the core of their business.

What is an e-signature platform?

An e-signature platform is a solution that allows users to electronically sign documents. This type of platform is popular in many industries including FinTech, gambling, ecommerce, SaaS, logistic, etc. In our very digital age, e-signatures remove the need for companies and customers to sign deals face to face, leading to highly customer conversions and satisfaction.

Although there are security issues around e-signatures, the industry has matured enough that there are standards and guardrails in place to protect both companies and customers from malpractice.

Normally e-signature platforms include features like document creation, editing and sharing, audit trails, brand customisation, and e-signing to name a few. They should also adhere to ESIGN, UETA, and eIDAS standards. Some tools provide workflow automation, id verification, integrations with CRMs and so much more.

Which e-signature software is free to use?

There are many e-signature software platforms that offer free plans for individuals and small businesses. Some popular options include HelloSign, DocuSign, and CocoSign. Free software will not allow API access. 

Which e-signature software is the easiest to use?

Formstack Sign, DottedSign, and Rocket Sign are all highly rated as easy to use e-Signature softwares on the market today. Of course bigger names like Foxit, Adobe and DocuSign are also known for their user-friendly products.

Which e-signature software is used for digital signature validation?

There are many e-signature softwares that can be used for digital signature validation. These would include, but are not limited to, GetAccept, Box Sign, and Adobe Acrobat.

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