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PDF API vs Workflow API

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By Mang-Git Ng

Learn about the difference between Anvil's PDF API and Workflow API, followed by a discussion on things to consider when selecting the API best suited for your needs.

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PDF API vs Workflow API

What's the difference?


The Anvil PDF API consists of three endpoints that simplify integrating PDFs into your application. These three endpoints are:

  • PDF generation - Generate brand new PDFs such as invoices.
  • PDF filling - Fill in any existing PDF template such as IRS form W-4.
  • Etch e-sign - Request signatures on PDFs from multiple parties.

With a single API request, you can prepare a signature packet by uploading a custom PDF and/or filling in an existing PDF template, and then request signatures from all signing parties.

It is called the PDF API because these endpoints operate directly at the PDF level.

For both the filling and generation API endpoints, there is no visible Anvil UI that is displayed in your application. Your application simply makes a web request to Anvil and Anvil responds with PDF byte code.

For the E-signature API endpoint, Anvil provides a signing UI that can be embedded in your application, presented in a modal, or redirected to a standalone page from your application.

Anvil Workflows

Anvil Workflows combines PDF filling, generating, and e-sign capabilities with an intuitive, web-based UI to collect information. The workflow builder allows anyone to quickly create an online experience that replaces offline paperwork processes or the need to manually develop online forms. The Workflow API allows you to programmatically interface with these workflows with seamless integration into your application. There are two flavors of Workflow APIs:

  • Workflow GraphQL - This is a powerful suite of endpoints for interacting with Anvil. Almost all Anvil interactions are available in the GraphQL endpoints. Start new submissions, track submission progress, lock and unlock submissions, void signature packets etc.
  • Workflow URL - This is a simple interface for creating new submissions to a workflow and pre-populating the workflow with data.

Depending on the level of integration and the complexity of your application, you can choose between the flexibility of the GraphQL endpoints and the ease of the Workflow URL endpoints.


Webhooks round out the Anvil developer platform. Webhooks can be registered for Anvil Workflows as well as the Etch e-Sign endpoint. The PDF filling and PDF generation endpoints are synchronous API endpoints, so webhooks do not apply for these endpoints.

Anvil webhooks allow you to be notified of certain events within the Anvil system. These include new submissions created, submissions complete, signings completed, and more. To get a full list of webhook events, take a look at the Anvil webhook documentation.

Which solution is right for me?

In selecting the best way to integrate Anvil via API, there are a couple of things to consider:

  • Application complexity
  • UI and UX ownership
  • Allocation of development resources
  • Pricing

Application complexity

Is the workflow you are automating a core value proposition of your product? What is the “secret sauce” of what you are trying to build, and where would you like that “secret sauce” to live?

Using Anvil Workflows can greatly accelerate your product development. If the business logic is simple or there is minimal proprietary code in your application, then using Anvil workflows can offload a lot of effort from your developers, allowing them to refocus their energy on building and improving core features. Using Anvil will help you build faster, and get to market sooner.

Alternatively, if there are proprietary algorithms, industry-specific integrations, or changing business requirements with various SLAs, then owning the workflow development cycle might be important to you. In this case, you can rely on Anvil as the PDF layer that integrates seamlessly into your existing development process.

In summary, if you require a high degree of control of the software, use the PDF API. But if you are pulling together multiple tools and the business logic is simple, Anvil Workflows are a great option.

UI and UX ownership

Is your company mainly innovating around creating a 10x better user experience? Is having a cohesive look and feel across all your customer touchpoints important?

When it comes to UI and UX, Anvil Workflows provide standardized UI components with pre-built validation. You can add custom validation but you cannot change the look and feel of each individual component. The goal is to provide a comprehensive foundation for building online forms, trading fidelity for speed. Think of the workflow platform as a higher-order software library that abstracts away the nitty-gritty of CSS styling, field validation, and component-level integrations such as Google Location API for address fields.

Alternatively, the Anvil PDF API sits in the background and operates via server-side web interactions. Other than the Etch e-sign view, there is no Anvil UI that is displayed, giving you complete control of your application’s look and feel.

Anvil Workflows can mean significantly less work for your development team at the expense of controlling the look and feel of your application. On the other hand, the Anvil PDF API is extremely simple to integrate but will require more work from your front-end developer.

Allocation of development resources

What is the best use of your time and effort? What area of expertise are your team’s skills best suited to?

When building an application, the last thing you want to worry about is wrestling with dependencies, deploying a new library, or fixing CSS styling. Hiring and recruiting teammates can be time-consuming and costly.

Anvil Workflows are easy to create, even for non-developers. You can bring on a team of operational specialists, people who understand the process, and empower them with the technical tools to build their own workflows.

The PDF API is unobtrusive, operates in the background, allowing your application to take center stage. The integration is simple but does require a deeper level of software development expertise, beyond the level of knowledge expected of non-engineers.

If you are technical, or you have a large developer team, then the PDF API is a viable option. If you are non-technical or are constrained in terms of developer resources, use the Anvil Workflow platform.


How much do you want to spend on third-party workflow tools?

Here’s how the PDF API pricing breaks down:

  • PDF filling or generation: Starts at $0.10 / completion
  • Etch E-Sign: Starts at $1.50 / completed packet (Can have multiple signers, includes filling or generation)

And here’s pricing for the Workflow platform:

  • Workflow: Starts at $1 / completed submission
  • Workflow w/ Etch e-Sign: Starts at $2.50 / completed submission
  • Workflow API endpoints: Free, unlimited requests

Inquire about bulk discounts for high-volume enterprises by emailing

Although on the surface Anvil Workflows are more expensive, they can actually be more cost effective in the long-run. Workflows are not billed per API request, only when a submission to the workflow is completed. The cost of developing an application from scratch can be much higher. With the Anvil platform, you can build the same application faster and with fewer developer resources.


The general rule of thumb: if you are adding PDFs as part of an existing application, or if you would like to retain posession over the business logic, UI or UX, then the PDF API is a good choice. The Anvil Workflow platform is a great option if you are looking for a fast way to deploy new workflows, want a consistent way to gather and interact with customer data, or are constrained on developer resources.

Even if you think the PDF APIs are the right choice for you today, we encourage you to explore our Workflow platform. Empowering non-developers on your team to build, deploy and manage their own workflows is an incredibly powerful paradigm shift in how businesses of the future will operate.

Whatever decision you make, Anvil’s goal is to provide a simple yet flexible platform to help you streamline paperwork and data-gathering for your business. Resources

If you have questions, please do not hesitate to contact us at

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