How to use the flatten pdf forms and annotations
- Choose a PDF or drop it on the box. A short line under the file name tells you how many form fields and which kinds of annotations were found.
- Tick what to flatten: form fields, annotations with a drawn appearance, or both. Tick remove clickable links only if you want the link areas gone as well.
- Press Flatten and download. The new file is named after the original with "-flattened" added, and a preview of page 1 appears so you can check it.
- Open the result in a PDF viewer and confirm that the values and marks are still visible and that the fields can no longer be clicked or typed into.
What flattening does
A fillable PDF stores each field as a small interactive object that sits on top of the page and draws its own appearance. Flattening draws that appearance onto the page itself and then deletes the interactive object. What you see stays the same, but nobody can change the typed answer or tick another box.
Stamps, highlights, ink drawings and free text notes work in a similar way. Each one has a stored picture of how it looks. The tool places that picture on the page at the position and size the annotation asked for, using the standard rule of mapping the picture box onto the annotation rectangle, and then removes the annotation.
What flattening does not do
Flattening is not redaction. If a black box was drawn over text, the text underneath is still in the file. It is also not a security feature and not a digital signature check. A signed PDF that is changed in any way no longer matches its signature, so flatten a copy and keep the original.
Annotations that have no stored appearance, such as some plain comment icons, cannot be drawn and are left as they are, and the result message counts them. Hidden annotations and pop-up windows are removed because there is nothing to draw. Links have no appearance, so they are kept unless you ask to remove them.
Tips for getting a good result
Fill in the form completely before flattening. If a field value contains characters the standard fonts cannot draw, the tool falls back to the appearance already stored in the file and tells you so. To combine flattened files, use merge PDF, and to check the document properties afterward, open the PDF metadata editor.
Assumptions and limits
- Only form fields and annotations that already carry a stored appearance can be flattened. Dynamic XFA forms are not supported and may flatten to blank fields.
- The pages themselves are not re-rendered, so text stays selectable and vector graphics stay sharp.
- The file is not encrypted or password protected. Protected PDFs are refused with a clear message.
- The original file is never changed. The flattened copy is built in your browser and downloaded.
Frequently asked questions
How do I make a filled PDF form impossible to edit?
Flatten it. The typed answers become part of the page and the fields disappear, so a viewer can no longer change them. Keep an unflattened copy in case you need to correct something.
Does flattening hide or remove the text under a drawn black box?
No. Flattening only fixes what is already on the page. Text covered by a drawn shape is still stored in the file and can usually be selected or extracted.
Why did some comments stay in my PDF?
A comment can only be flattened if the file stores a picture of how it looks. Comments without one are reported in the result message and left untouched.
Will flattening make my PDF smaller or larger?
Usually the size changes only a little. Removing fields saves a few bytes, while drawing appearances onto pages adds some page content. Large changes are unusual.