Which flatten PDF mode should you pick?
| Form fields | Whole pages | |
|---|---|---|
| What becomes fixed | Filled form fields | Everything: fields, comments, highlights, stamps, drawings |
| Text selectable and searchable | Yes | No, each page is an image |
| File size | About the same | Can get bigger |
| Best for | Forms you send or archive | Final copies nobody should edit |
Form fields is the default and suits most filled forms. Choose Whole pages when the markup itself matters, for example a reviewed draft full of comments, or a drawing with approval stamps. Pick 300 DPI if the pages will be printed, and 150 DPI to keep the file smaller.
When to flatten a PDF form
Flatten a form right before it leaves your hands. Good moments include:
- Emailing a filled application or registration form, so the receiver sees your answers, not empty boxes.
- Saving a completed form for your records, so the values cannot change by accident.
- Sharing a teacher's or editor's comments as a fixed copy that keeps every note visible.
Keep the unflattened original if you might need to correct an answer later. Once a form is flat, the fields cannot be typed into again. Check spelling, dates and ticked boxes before you flatten, since a mistake then has to be fixed in the original and flattened again.
Flattening with other PDF tools
Crop PDF hides what is outside the crop box but does not erase it from the file. Run Whole pages mode afterwards so the hidden part is really gone.
The same goes for a stamp from Watermark PDF: on its own it sits on top of the page and a PDF editor could remove it. Whole pages mode makes it part of the page image, so it cannot be lifted off. If the result is too heavy, try Compress PDF.