10 Best Free and Open Source Digital Signature Software 2021

Documentation is the backbone of business. Influencing internal processes, external communications, and agreements at every level—it’s an area of communication that impacts every aspect of an organisation. Yet, many firms have struggled to modernise the way they handle paperwork.

Digital signature software and modern processes have the potential to revolutionise how efficient and secure a business can be. A digital signature is easier to trace, easier to audit, faster to use, and cheaper to store than traditional paperwork. Physical documentation, in contrast, is cumbersome, expensive, and time-consuming to maintain.

The additional challenges imposed by an increasingly distributed workforce and global network of partners escalate these issues even further.

The financial costs and environmental impact of shipping, storing, and producing paper documentation are something businesses should be targeting today as unnecessary overhead.

Digital signature software is a solution that tackles the problems of authenticating and approving vital documentation. In addition, it provides a more manageable workflow than paper-based models and creates a robust and reliable way of distributing, securing, managing, and auditing business-critical documents.

At its core, a digital signature provides an authentication and security layer on top of a digital document. Whether PDF, word document, vector graphic, or something else—a digital signature ensures the integrity, authenticity, and authorship of any.

Are Digital Signatures Legally Binding Worldwide?

In short: yes. More than 60 countries have enacted legislation that equates electronic signatures and digital verification to a “wet signature” written with pen and paper.

• In the European Union, European Directive 199/93/EC legislated for digital signatures within the EU since mid-2001
• In the United States, the Electronic Signatures in Global and National Commerce Act of June 2000 ensured contracts signed with e-signatures were legally binding and equivalent to existing paperwork
• In the United Kingdom, the Electronic Communications Act 2000 and Electronic signatures regulation 2002 ensure that digitally signed documents remain legally equivalent to paper copies
• Australia, China, India, Japan, and New Zealand are among countries that have adopted similar legislation to protect digital signatures specifically.

A much larger and continually growing list of countries has adopted legislation of their own to enact laws that specifically protect digitally signed documentation.

What Is a Digital Signature?

To understand how a digital signature works and what makes it more secure than paper-based versions, you first have to know a little about public-key encryption.

Often referred to as asymmetric encryption, public-key encryption assigns every user with two keys to their personal key-chain. One of these keys is kept private, and despite never being publicly revealed, provides a vital means of proving your identity to another party. The second key is public, shared with the world; it may be included in your email footer or your personal web page. The public key is used to verify the identity of your private key without ever needing to disclose it at all.

When a client digitally signs a document, it’s first put through a one-way hashing function—a mathematical operation that produces data that auditors or users can verify against the file later. The resulting hash is then encrypted, using the client’s private key, and digitally signed with a certificate from a known and trusted certificate authority (CA).

The output of this process should be a digitally signed document that verifies the document’s contents, metadata, and signer.

It’s important to note here that the document itself is not encrypted at this stage—only the verified hash. A digital signature alone does not provide confidentiality, though this can be added at a later stage by most digital signature software.

To verify a signed document, the digital signature need only be decrypted with the client’s widely available public key and compared to the hash of the original data to prove that no modification or tampering has taken place.

Throughout the process, both parties have clear evidence that the document has been signed by an authenticated party and that its contents remain unchanged. At no stage has the signer had to reveal their private key, meaning the key pairing brought into the transaction can be reused indefinitely.

Many highly regulated fields and institutions in finance, medicine, and defence use digital signature software routinely to prove the authenticity, integrity, and authorship of their documents.

What Does Digital Signature Software Do?

The role of digital signature software is to provide an accessible route to using public key infrastructure (PKI). Designed to take the burden out of managing public keys, high-quality digital signature software should provide a route to signing documents in a matter of seconds once fully set up.

The core features of a digital signature software package should include both the signing and verification of documents using public-key encryption. The primary result of the process should be an embedded audit trail associated with the document that is easy to access and verify.

Advantages of a Digital Signature

Aside from the advantages in security, integrity, and verification outlined here—a digital signature can deliver a great deal more to businesses in the way they manage their workflows and practices.

• Document transfer. It’s now more common than ever for businesses and staff to be separated from one another and working towards a common goal. Digital signature software reduces the financial and time burden of shipping documents between offices and staff.
• Reduced costs. The equipment, stationary, and storage costs of paper-based documentation are trivially easy to cut.
• Reduced environmental footprint. The impacts of generating, shipping, and storing documentation add up fast. Cutting back is an easy way to reduce the impacts of your firm.
• Easy to restore. Digital documentation is trivial to back up and can be done so on a regular basis. Organised file management reduces the number of opportunities there are for paper documents to be left on a desk, lost in the mail, or filed and forgotten in error.
• Ease of distribution. A digitally signed document can be distributed to any number of clients or shareholders without requiring dozens or hundreds of signatures at a time.

Combined with the additional layer of security added by public-key encryption and the ease at which a digital signature can be audited and verified—it’s becoming increasingly difficult for modern businesses to justify the maintenance of paper-based resources.

Key Features of Digital Signature Software

There are a wide array of digital signature software packages available. Current solutions range from small stand-alone programs focused on the core essentials—to large document management systems that provide a comprehensive management package. These suites often enable users to annotate and edit documents, add branding, and track their electronic documentation.

From a business perspective, some of the core features to look out for in digital signature software should include:

• Time Stamps. A key part of a verifiable digital signature includes an accurate and verifiable time stamp. These may also determine how long a document and signature is valid for and how long additional parties may have to sign.
• Embedded auditing. It should be possible for users to verify the contents of a document and the previous signatories, metadata, and history associated with the file.
• Public key infrastructure standards. A digital signature solution should comply with PKI standards that set the requirements necessary to ensure a digital document is authored and signed securely. These include reference to the encryption standards used and Certificate Authority relied upon for the signing transaction.

In addition to these core requirements, digital signature software solutions may include features and functionality that make managing your documentation easier. These can often come with some more advanced or more complete packages that create an entire documentation workflow.

Designed to make your documentation processes more streamlined and efficient, they can take some time to learn but also provide a much-needed boost inefficiency.

Some secondary features of digital signature software can include:

• Document tracking. View when a document has been opened, shared, and reviewed by shareholders. A useful way to determine when to follow up on pending paperwork
• Document management. Capable packages can separate out documentation still pending signature, those still to be signed by third parties, and those held up by external factors
• Summary report. Providing a comprehensive summary of evidence for digitally signed documentation
• Branding. Many packages include options to implement corporate branding on documentation as a way to both further protect signed documents and create a consistent look and feel across the duration of a project

Let’s discuss the best digital signature software on the market

1. SignServer

SignServer is a lightweight digital signature solution that is more than capable of handling the needs of small to mid-sized businesses. The focused yet flexible approach to document signing SignServer enables the software to be integrated into most workflows and suit a wide range of use cases.

Featuring a strong and robust set of core document signing features, SignServer additionally supports code signing for Microsoft Authenticode, Android APKs, and generic Java packages.

(Source: SignServer)

Top Features:

• Allows users to add a digital signature to code and documents
• Lightweight application design focused towards document signing
• Verification for digitally signed documents and files
• Signs PDF and XML documents
• Secure key management for multiple signatures
• Extensive discussion forums for application support
• Capable of creating visible and hidden signatures
• 3rd party integration support
• Regular training courses available and enterprise support for advanced users

2. OpenKM

OpenKM is a fully-featured open sourced document management suite. Often referred to as a Document Management System (DMS), OpenKM can be used to store, manage, and track both electronic documents and digital copies of paper-based files.

The philosophy behind the OpenKM DMS is in building a repository of commercial data, assets, and knowledge capable of improving decision making and productivity. As a robust DMS, OpenKM includes extensive features and support for signing documentation, tracking digital signatures, and managing public key infrastructure as part of its extensive functionality.

Top Features:

• Create an entire document workflow that includes task management, digital signing, and document protection
• Exceptionally well-documented features and packages
• Provides a comprehensive activity log and reporting tools for auditing and verifying signed documentation
• Third-party integrations are available for a wide range of services and platforms
• Included OCR engine enables extracting content from scanned paperwork and documents to digitise physical files
• Can be used independently to digitally sign documents or to create a much larger workflow for records management

3. iSafePDF

iSafePDF is a stand-alone application designed to allow you to digitally sign PDF documents. Exceptionally lightweight and focused, iSafePDF is built to integrate with almost any workflow by creating minimal intrusion or interruption.

Despite being so singularly focused, iSafePDF has a rich set of features that make it a critical addition to the toolbox.

Top Features:

• Certificate verification and signature auditing
• Allows for customised text and branding on the visible signature
• Offers PDF password protection with robust encryption for protected documents
• Excellent tools for PDF editing and meta-data editing on documents
• Detailed reporting available for signed documents

4. AltoSignPDF

Alto Sign PDF is a web-based application for digitally signing documents. Exceptionally simple to use, the drag & drop interface allows users to upload documents to the service or import them from cloud storage for digital signing.

Somewhat unique amongst the free solutions on our list, Alto Sign offers unlimited signatures and storage to users and enough conversion tools and resources to support almost any type of required documentation.

Top Features:

• Supports document conversion to and from PDF for a wide array of formats
• Supports PDF editing through the web browser interface
• Available at the web page, browser extension for Google Chrome, or mobile apps for both Android and iOS
• Unlimited cloud storage for user documents
• Enables document watermark to add custom branding to resulting documentation
• Extensive support available

(Source: AltoSignPDF)

5. JSignPDF

Similarly focused to the stand-alone applications included in our list, JSignPDF is an open-source application for adding digital signatures to PDF documents. Executing the core functionality of digital signature software exceptionally well, JSignPDF offers a rich range of options, including batch processing and PDF protections.

JSignPDF provides both its Java-based application and an extension that integrates with OpenOffice.

Top Features:

• Visible signature uploaded from an image or file
• Add hidden signatures to PDF documents
• Customisable certificate levels
• Certificate validation through CRL and/or OCSP
• PDF encryption and rights protection
• Support for batch processing, command line accessibility, and GUI control
• Extensive high-quality documentation

6. Xolido Sign

Xolido Sign provides a highly dependable document signing application for a wide variety of documents and file types. Xolido’s software exists as a stand-alone application for signing and verifying documents with extensive and flexible reporting options available.

(Source: XolidoSign)

The application boasts a great deal of documentation, learning resources, and free technical support. With various versions of the package available, it’s a suite available to grow and evolve alongside your business.

Top Features:

• Capable of adding a digital signature to PDF, Word, Excel and txt documentation in addition to almost every kind of digital file type available
• Keeps a detailed report of document signings and processing receipts
• Extensive documentation and technical support available
• Extended versions available for large scale businesses looking to do more
• In production since 2010, it’s a well-tested and highly dependable solution

7. DottedSign

(Source: DottedSign)

DottedSign is a cloud-based digital signature software solution designed to allow users to sign and verify documents from any device or location. The package includes simple document management tools and organising features that help you to track signed and unsigned documents and assist with following up on progressing documentation.

With a philosophy centred around creating a smooth and efficient way to integrate digital signatures and document management into your existing workflow—few solutions can be adopted so easily or seamlessly into your organisation.

Top Features:

• Designed around web and mobile, easy to use on the go
• Includes one-time pass features to verify signers identity (using email or SMS)
• Allows other input types, such as a checkbox or radio button, to be added to forms
• Automated document delivery features
• Extensive audit trail for signed documents
• Centralises document management to a single cloud-based solution

8. DocHub

Offering a streamlined document signing and distribution solution, DocHub provides integration with popular cloud hosting platforms in addition to its core digital signature software functionality. The platform’s unique software package comes with a powerful suite of annotation and form editing tools to allow document markup and editing on the go.

Included amongst DocHub’s strongest features is the ability to edit PDFs online and the capability to sign and verify documents through the web interface or mobile device.

(Source: DocHub)

Top Features:

• Supports a near-universal array of document formats
• Intuitive interface and guide to take recipients through the document signing process
• Annotation tools to markup documents for editing and review
• Collaborate with colleagues through the web interface
• Support for a wide array of languages
• Free tier allows for 5 document signatures a month and 3 document requests
• Upgradable to include more extensive tools and an unlimited number of signatures, signing requests, and documents

9. E-signly

E-signly provides a web-based digital signature software platform for signing, sending, and authenticating digitally signed documents. Built using Amazon cloud, it’s ideally suited to signing and sharing documentation with trusted partners and colleagues.

Amongst the strongest features of E-signly are its ability to integrate with cloud-based storage platforms such as Dropbox, Evernote, Google Drive, and OneDrive. Additionally, E-signly comes with one of the most extensive suites of tools available for facilitating team management, branding, notifications, and workflow management.

Top Features:

• Customisable branding on documents, forms, and emails
• API for integration with existing workflows and tools
• Includes document management tools to provide granular access and editing controls
• Allows the creation of templates for customised documentation requirements
• Tools to support scheduled, in-person, and self-signing documents
• Free tied allows for signing three documents per month

10. Hellosign

HelloSign provides a complete web-based document management system. Designed to facilitate not just signing but also sharing, editing, and collaboration over documentation. The free tier of HelloSign includes enough templates, signatures, and sign requests for small to mid-sized business use.

Notably, HelloSign includes a comprehensive audit trail for documentation, exceptional cloud storage integration, and a technical support team to troubleshoot any arising issues.

(Source: Hellosign)

Top Features:

• Includes an audit trail and detailed reports to ensure every action in relation to the document is time-stamped and tracked
• Supports the creation of documentation templates for regularly used and highly customised documents
• Integrates with cloud storage solutions to easily access and share documentation
• Includes the ability to create additional form fields to capture checkbox input, buttons, and dates
• Includes a mobile-friendly signing solution for documentation
• Supports typing, drawing or uploading a visible signature onto documentation
• Extended tiers include one-time pass functionality, SMS authentication, and advanced business-friendly features

Modernising Business Documentation

Documentation is a vital requirement of modern business. There’s little today that can be done without it. More importantly, it’s a valuable resource to draw on in legal disputes, agreements, and things as small as aligning the goals and objectives of team members.

A digital signature provides an added layer of trust, security, and authentication to your documentation. It provides assurances and evidence that even a traditional ‘wet signature’ simply can’t provide.

Digital signature software today is doing more than merely providing cost savings, convenience, or accessibility—it’s creating a robust and reliable framework to bring paperwork into the 21st century.