A filled form is a promise written in pencil: its answers sit in editable fields, and anyone with a reader can change “Yes” to “No” without leaving a trace. Flattening is the ink. It converts a form's fields into ordinary, fixed page content and removes the fields themselves — after flattening, the answers are simply what the page says. This tool does it properly, in your browser, and tells you exactly what it flattened.
What flattening really does
In a live form, a field's answer exists twice: as data (the value) and as a picture (the appearance the form generates so readers can display it). Flattening keeps the picture and discards the machinery — the field is removed from the document's form layer and its appearance is painted into the page's own content, with pdf-lib (an open-source library running locally in your browser) doing the surgery. Text in the answers remains genuine text: selectable, searchable, crisp at any zoom. The result is a normal document that prints identically everywhere and cannot be casually re-edited — which is why flattened copies are the ones you send out, archive and sign off. Your original stays untouched, fields and all, in case the answers ever need revisiting.
Two methods — and they are not the same
Form fields only (the default, and the true meaning of flatten) touches nothing but the fields. It is fast, lossless, and reports the exact field count it flattened; a document with no fields is told “nothing to flatten”, because for it, nothing is true. Everything, as page images is the heavy route offered by some flattening services: every page is re-rendered as an image at 200 DPI and the document is rebuilt from those pictures — the same honest rebuild the Compress tool performs. Fields, annotations, stamps, vector art: all baked in. But the price is real — text becomes pictures (unselectable, unsearchable), quality is capped at the render resolution, and file behaviour changes throughout. Use it only when “absolutely everything frozen” is genuinely the requirement.
When to flatten — and when not to
Flatten the copy you send: the completed application, the signed-off timesheet, the form going into an archive or a court bundle, where “the answers as submitted” must be a fixed fact. Do not flatten the only copy you keep: once fields are gone, correcting a typo means re-filling from scratch (or going back to your unflattened original — which is why this tool always works on a copy). And note what flattening is not: it is not a signature, not encryption, and not redaction. It makes a form's answers read-only; it does not control who can open the file (that is the PDF Lock Tool) or remove hidden content.
Private by design
Like every CalcViso file tool, this one runs entirely in your browser. The file you choose is read by this page, processed on your device, and offered back as a download — it is never uploaded to a server, never stored, and never seen by anyone else. Close the tab and it is gone from memory.
Worked example
Press the sample button: the tool builds a small form with the name “Ada Lovelace” already filled and a checkbox already ticked — 2 fields, as the stats confirm. Press Flatten PDF with the default method and open flattened.pdf: the name and tick still show, but clicking where the fields were does nothing — there are no fields left, and selecting the name copies it as ordinary text. Run the same sample through the image method instead and the difference is tactile: nothing on the page can be selected at all.
How to use this tool
- Drop your PDF onto the box (or create the filled sample form); the stats show how many form fields were found.
- Choose the method: form fields only for a true flatten, or the image method when everything must be baked in.
- Press Flatten PDF and read the result line — it reports exactly how many fields were flattened, or that there were none.
- Download the flattened copy and open it: try clicking an answer. In the form method it selects as text but cannot be edited; the fields are gone.
- Send or archive the flattened copy; keep your original, still-fillable file somewhere safe.
Flattening and signatures
Forms often end with a signature, and the order of operations matters. Fill first, sign second, flatten last: Fill PDF Forms puts the answers in, Sign PDF places a visual signature over the page, and flattening then fixes the field answers around it. One honest caveat — flattening does not protect a signature image from being copied out of the file, any more than ink on paper prevents a photograph of the page. Flattening fixes content; questions of proof and identity belong to cryptographic digital signatures, which browser tools do not provide.