This page does two related jobs. Fill completes an interactive PDF form: every field in the document appears as an input with its current value, and you download the result either still editable or flattened. Flatten locks a PDF you already have, without filling anything — either by fixing its form fields in place, or by rasterizing every page into an image.
Drafts vs final submissions
The one decision that matters most is whether to flatten. Think of it as the difference between a draft and a final copy:
- Keep it editable (don’t flatten) while the form is still in progress — when you need to come back to it, send it to a colleague to complete their section, or aren’t sure of a value yet. The downloaded PDF stays fillable.
- Flatten when the form is done and you’re submitting or printing it. Flattening bakes your answers into the page and removes the interactive fields, so no one can change your entries through the form and the document renders identically in every viewer.
A common mistake is sending a non-flattened form for a formal submission — the recipient (or their PDF software) can still edit the fields, which is rarely what you want on a signed application or contract.
Two ways to flatten, and what each one locks
Form fields and annotations live in separate, interactive layers above the page. The two flatten methods reach different layers:
| Flatten form fields | Rasterize | |
|---|---|---|
| Typed answers, checkboxes, dropdowns | Fixed into the page | Fixed into the page image |
| Comments, highlights, sticky notes, stamps | Left as they are | Fixed into the page image |
| Text selectable and searchable | Yes | No |
| File size | About the same | Usually larger |
Use Flatten form fields for a completed form you still want to be searchable. Use Rasterize when the document must look identical everywhere and nothing on it should be selectable, copyable or editable — at the cost of search and a larger file. Either way the result is permanent: keep the original if you might need to change an answer later.
Why “no upload” matters more here than usual
Forms are, by definition, where you put the sensitive stuff: full name, address, date of birth, account and policy numbers, salary, medical details. Uploading a half-completed tax or HR form to an online filler means that data sits on someone else’s server, however briefly. Because both modes parse and write the PDF entirely in your browser — pdf-lib for filling and form flattening, PDF.js for rasterizing — the document never leaves your device. You can confirm it by filling a form with your network disconnected; it still works.
When this tool isn’t the right one
Fill completes existing form fields. If your PDF is a flat scan or an exported document with no interactive fields, there’s nothing to fill — the tool tells you so rather than failing silently. For those, you want to place text and a signature on top of the page instead, which is what a PDF signer does. And if your form is locked with a password, unlock it first, then come back here.