Guide
Filling a PDF form and locking the answers in
A fillable PDF form has interactive fields on top of the page: boxes you click into, checkboxes, lists. They’re convenient to fill, but they stay editable after you send the file, some viewers don’t display them, and some upload systems drop them. Flattening takes the current answers and paints them onto the page, then removes the fields. The form looks exactly the same, but it behaves like a printed and scanned copy.
Filling the form
Open the PDF and every field appears in a list, grouped by page:
- text boxes, including multi-line ones, respecting maximum lengths,
- checkboxes,
- radio buttons, with a “None” option to clear a choice,
- drop-down lists and multi-select lists.
Labels come from the field’s tooltip where the form’s author added one (often the clearest description), otherwise from its internal name. Answers already in the file are shown, so you can correct a single field without retyping the rest. Read-only fields are listed but can’t be changed.
Flatten, or keep it fillable
With Flatten on (the default), each answer is drawn onto the page and the fields are removed. Turn it off to simply save the filled form: the answers are stored and their appearance is updated, but the fields stay editable for the next person.
Typical reasons to flatten:
- an office or court asks for a “non-editable” or “flattened” copy,
- the form will be merged with other documents,
- you want the answers visible in every viewer, including phone previews.
Fonts and characters
Answers are drawn with Helvetica, the standard font of PDF forms. It covers English and Western European languages, including accents such as é, ü and ñ. If an answer contains characters from other scripts, the tool stops and explains, rather than producing blank or garbled text. In that case, keep the form fillable and fill it in a reader that has those fonts, or print and scan it.
XFA forms
Some government and corporate forms are built with Adobe LiveCycle (XFA). They contain two descriptions of the form, and many readers only understand one of them. The tool fills the standard fields and removes the XFA layer, so every reader shows the same answers. Highly dynamic XFA forms, which add sections as you type, may lose that behaviour.
What flattening doesn’t do
- It doesn’t sign the document; add a visible signature with Sign PDF before or after.
- It isn’t security: anyone can still edit a flattened PDF with editing software. To control access, use Protect PDF.
- It doesn’t remove comments and highlights; use Remove PDF Annotations for those.
When there are no fields
Many forms only look fillable: they’re scanned or designed without real fields. The tool tells you when a PDF has none. Type onto such forms with Edit PDF, which places text wherever you click.
Forms stay on your device
Application, tax and medical forms are full of personal data. Filling and flattening run in your browser; the form and your answers are not uploaded.
A worked example: a rental application form
A tenant receives a fillable application form and must return a non-editable copy.
- Open the PDF; 24 fields appear, grouped over three pages, with the agent’s tooltip labels.
- Fill in name, address, income and the checkboxes; choose the move-in month from the drop-down.
- Keep Flatten on and click Fill and flatten.
- Sign the flattened copy with Sign PDF and send it.
Checked against the current version of the Fill & Flatten PDF Forms on .