You've signed a PDF and someone tells you to flatten it before sending. It sounds violent, but it just means baking everything into the page — fields, signatures, annotations and all — so nothing can be edited later.
What flattening actually does
A PDF can carry layers: form fields you can edit, signature widgets, sticky notes, comments. Flattening merges all of these into the underlying page, the way a chef folds ingredients into batter. After flattening, your typed answers and signature are part of the page itself. They look identical, but they're no longer separate, editable objects.
Why you'd want to
Two reasons. First, security: a flattened PDF can't be tampered with as easily — no one can rewrite your filled-in answers. Second, compatibility: some older systems strip out form fields or render them oddly. Flattening avoids the surprise. If you're signing a PDF for a contract, flattening afterwards is a common and sensible final step.
What you give up
Once flattened, you can't change the answers or remove the signature without starting over. So flatten only when you're sure the document is final. If you might need to tweak it, keep an unflattened copy. Flint lets you edit a PDF before flattening, then export a sealed version when you're ready to send.
FAQ
Can a flattened PDF be unflattened?
Not really. Flattening is a one-way operation — the layer information is gone. If you need to edit later, work from your unflattened backup or rebuild the fields from scratch.
Does flattening protect a PDF from editing entirely?
It stops casual tampering with fields and annotations, but a determined editor could still overlay new content. For stronger protection, combine flattening with a password or a digital signature.
Do I need to flatten before printing?
No — printing automatically renders all layers onto the page. Flatten when you're saving and sending the digital file, not when printing.
Need to finalise a signed PDF? Sign it in Flint and you can export a flattened copy in one go.