What is PDF form flattening?
Flattening a PDF form merges the filled-in field values into the page content itself. After flattening, the fields are no longer editable — the values become part of the document permanently, and the file opens identically in every PDF reader.
Why flattening matters
An unflattened PDF form still has editable fields. Anyone who opens it can change the values, even after you've filled it in. For visa packets, government submissions, HR records, and insurance claims, that's a compliance risk. Flattening removes the editable structure and bakes the values into the page, so the recipient receives a final, locked document.
Flattening and signatures
Flattening is also where many filling workflows go wrong with signatures. If you flatten a PDF that already has a digital signature, you can break the signature's cryptographic link to the document content. The fix is sequencing: fill, flatten, then sign — or use a signing tool that handles the order itself.
Flattening for scanned forms
When the source PDF is a flat scan, the only way to add values is by overlaying them as a separate layer on top of the page image. Flattening then merges that overlay into the image, producing a single composite that looks identical to a hand-filled scan and opens in any reader without dependencies.
How FillWizard flattens by default
Every export from FillWizard is flattened. The values you filled — whether onto AcroForm fields or as overlays on a scan — get merged into the page content. The output is a portable PDF that opens identically in Acrobat, Preview, Chrome, and on mobile, with no editable field artifacts left behind.
Related terms
- AcroFormAcroForm is the original PDF form technology built into Adobe's PDF specification. An AcroForm PDF embeds fillable field objects — names, types, positions, default values — directly inside the PDF structure, so any modern PDF reader can detect and fill them programmatically.
- OCR for PDFsOCR (optical character recognition) converts text inside an image — like a scanned PDF — into machine-readable text. For PDF forms, modern OCR pipelines also detect field boundaries, checkboxes, and signature regions, so a flat scanned PDF becomes fillable.