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.
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 this tool parses and writes the PDF entirely in your browser with pdf-lib, the document never leaves your device — you can confirm it by filling a form with your network disconnected; it still works. For a task this routinely personal, local processing isn’t a nice-to-have, it’s the point.
When this tool isn’t the right one
This fills 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 will tell you so rather than fail 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.