What Flatten PDF does
Flatten PDF turns the interactive parts of a PDF — form fields, comments, annotations — into ordinary page content. A flattened form looks the same but can no longer be edited, and it displays consistently in every viewer and on every printer.
How to flatten a PDF
- Add your PDF. The tool tells you how many form fields it found.
- Choose what to flatten: form fields only, or everything.
- Press Flatten PDF and download the result.
The two modes
| Form fields | Everything | |
|---|---|---|
| What it does | Writes each field's value onto the page and removes the field | Redraws every page as a single image |
| Text selectable | Yes | No |
| Comments and annotations | Left as they are | Locked into the page |
| File size | About the same | Usually larger |
| Use it when | You have filled a form and want to lock the answers | You must be sure nothing can be changed, moved or hidden |
Why flatten at all?
- To lock a filled form. After flattening, nobody can alter your answers by clicking into a field.
- For reliable display. Some viewers, especially phone apps and browser previews, show fillable fields as empty. Flattened values are part of the page and always appear.
- For reliable printing. Print services sometimes skip form fields and annotations.
- Before merging. Two forms with identically named fields can overwrite each other's values when merged. Flatten them first, then use Merge PDF.
- To make comments permanent. The everything mode bakes sticky notes and mark-ups into the page.
When not to flatten
If the organisation receiving a form reads the field data electronically, or someone still has to complete part of it, send it unflattened. Flattening cannot be undone, so always keep the original fillable file.
Good to know
- With the everything mode, pages become images. Text cannot be searched or copied afterwards, and small print is slightly softer. Run PDF OCR on the result if you need searchable text again.
- Flattening is not redaction. Content that is visible stays visible. To remove sensitive information, use PDF Redactor.
- If a form cannot be flattened in form-field mode, the tool tells you; the everything mode works on any PDF.
Typical workflow
- Fill the form with PDF Form Filler.
- Sign it if required.
- Flatten it.
- Compress or merge it with enclosures and submit.
Privacy
Flattening happens in your browser. Your PDF is not uploaded to our server.
