Flatten PDFs.
Keep Your Data.
Interactive forms are great until you need to send them. Flattening a PDF bakes the form fields into the document itself so they can't be changed. We do it instantly, in your browser, without ever uploading your file.
Drop your PDF here
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Your file never leaves your computer.
Why you must flatten forms
If you've ever filled out an interactive PDF form, saved it, and emailed it to someone—only for them to open it and see a blank document—you've experienced the unflattened PDF problem.
Interactive PDF forms (AcroForms) store their data in a separate layer from the visual document. When you open an unflattened form in Apple Preview, a web browser, or third-party PDF readers, they often fail to render this layer correctly, resulting in blank fields or corrupted data.
Flattening merges the form data directly into the visual page layer. The fields cease to be editable form fields and become regular text on the page. It's the digital equivalent of printing the filled form and scanning it back in—but without the quality loss.
The Browser Security Advantage
Most online PDF tools upload your sensitive documents—tax forms, contracts, medical records—to their servers. They process them in the cloud, store them for "an hour", and then offer a download.
We do not do that. This tool uses modern web APIs (WebAssembly and ArrayBuffers via pdf-lib) to manipulate the binary data of your PDF entirely within your browser's memory. If you disconnect from the internet after loading this page, the tool will still work perfectly.
Common Mistakes
- "Print to PDF": Often strips interactive elements or degrades image quality. Flattening preserves the exact original vector rendering.
- Using Apple Preview: Saving forms in Preview notoriously corrupts AcroForm data for Windows users.
- Uploading sensitive data: Using cloud PDF tools for tax documents is an unnecessary security risk.
Technical Details
| Library | pdf-lib v1.17.1 |
|---|---|
| Processing | Local (Client-side) |
| File Limit | Browser RAM limit |
| Cost | Free, no ads |
Frequently Asked Questions
Can a flattened PDF be unflattened?
No. Flattening is a destructive process that permanently converts form fields into static text. You should always keep a copy of the original, unflattened file if you need to edit it later.
Does this tool reduce file size?
Often, yes. By removing the complex interactive form logic and dictionary objects, the resulting flattened PDF is typically smaller and parses faster in PDF readers.
What about digital signatures?
Flattening a signed PDF will invalidate the digital signature because the cryptographic hash of the document changes. If you need to preserve a signature, do not flatten the document.