An essential PDF SDK feature checklist for your next project

Choosing the right PDF SDK can feel overwhelming. You want just enough features to get the job done—without extra complexity or high costs. Here’s a simple checklist of essential features to look for in a PDF SDK, along with key questions to ask vendors during your evaluation process.

TL;DR: If you’re building something with JavaScript or React and need to work with PDFs, don’t just grab any tool that says it can “handle” or “fill” PDF forms. This article shows you the must-have features a good PDF SDK should include—like validation, data control, UI customization, native embedding, load, PDF-to-JSON, and various other features. It also explains why some tools make things way more complicated than they need to be, and how the right PDF SDK can save you tons of time. Every selection is followed with practical questions to ask vendors during your discovery phase. The big idea: pick a tool that feels like it belongs in your app, not a workaround.

I want to preface this article by stating that it outlines the minimum features and capabilities needed for PDF form filling use cases. However, many of these features may also be relevant for other PDF-related tasks, such as PDF viewing, annotating, and more. Let’s dive in to these features that are organized below by category.

Core PDF form-filling features

Your PDF SDK must handle basic form tasks smoothly. The most important things you’ll need are:

• Validation: Good PDF SDKs should support real-time form validation to ensure users enter the correct data before submission. This includes enforcing formats (e.g. phone numbers, dates), required fields, and conditional logic directly in the form layer.

• Data Control and Synchronization: It should allow seamless data flow between the PDF form and your application’s backend or database. This means supporting two-way data binding—when a user enters data into a PDF form, it should instantly update your app’s data model, and vice versa. Ideally, the SDK should also support structured data input/output (e.g. JSON) to programmatically populate fields and extract responses, ensuring consistency and reducing manual overhead in keeping data in sync.

Question to ask your vendor: "Can I control the data to and from various form fields using JSON?"

Frontend customization and UI

A good PDF SDK doesn't force you into rigid design patterns. Instead, it provides flexibility:

• Customizable UI Components: Look for an SDK that allows you to style form elements to match your application perfectly. You should be able to easily change fonts, colors, and layout using simple CSS.

• Customizable and Flexible UI: Your PDF SDK should have minimal, clean default designs that don’t interfere with your existing app style. You should also have full control over the appearance and feel of the UI through theming, making sure it looks and feels like a natural part of your app.

• Native Embedding Support: Choose a PDF SDK that allows native embedding directly into your application, rather than relying on iframes. Native rendering ensures better performance, responsiveness, and compatibility across web and mobile platforms.

Question to ask your vendor: "How much control do we have over customizing form elements to match our existing app design, and does your SDK support true native embedding without iframes?"

Performance and integration simplicity

How your PDF SDK performs and integrates with your app matters. Make sure you get:

• Lightweight and Fast: Choose an SDK that's small in size and loads quickly. A lightweight PDF SDK won't slow your app down, helping to keep your users happy with fast performance. For example, techniques like lazy-loading PDF assets, minimizing JavaScript bundle size through tree-shaking, and compute-heavy operations like rendering or parsing. Efficient memory management and asynchronous processing also help handle large files without blocking the main thread or degrading UI responsiveness.

Question to ask your vendor: "What's the typical size of your SDK for my use case?"

Export and submission handling

At some point, your users will finish filling out forms. Your PDF SDK needs to handle data export smoothly:

• PDF-to-JSON Export: Your SDK should allow easy extraction of data entered in forms into JSON format. This makes it simple to use or save data in your application's database or backend.

• Reliable PDF Generation: You should be able to generate high-quality, standardized PDF documents (PDF/A compliant), ensuring compatibility with many PDF viewers and readers.

Question to ask your vendor: "Can your SDK reliably generate standardized PDFs and export form data as JSON?"

Developer-friendly experience

Finally, a great PDF SDK respects developers’ needs:

• Transparent Pricing: Your PDF SDK provider should clearly state pricing with no hidden fees. You shouldn’t have to guess or worry about surprise costs. Predictable pricing helps manage your budget effectively.

• Helpful Resources, Support, and SLAs: Choose an SDK with plenty of examples, clear documentation, and responsive support. Quick help from real people can make integration faster and easier.

Question to ask your vendor: "Do you offer clear, predictable pricing and responsive developer support with practical examples?"

Why these features matter

A narrowly scoped PDF SDK focused on these core features allow for faster implementation and easier debugging. This lets developers maintain better control over the user experience and product maintenance.

This checklist offers a technical baseline for evaluating PDF SDKs that support form-filling. Focus on essential features like field mapping, UI flexibility, performance, and clear export mechanisms. Confirm that documentation is thorough and integration steps are clear.

By concentrating on tools that align with these core criteria, teams can improve reliability, reduce bloat, and accelerate release cycles without sacrificing PDF functionality. Happy building!

Need to build PDF form capabilities inside your SaaS application? Joyfill makes it easy for developers to natively build and embed form and PDF experiences inside their own SaaS applications.