UtilibyWritten by the Utiliby editorial team · Last updated October 13, 2026 · Rules and formulas reviewed October 2026
What this free PDF flattener does
A PDF is more than a picture of a page. It can carry form fields that you can type into, annotations such as highlights and sticky notes, stamps, signatures fields and optional layers. All of these sit on top of the page content and can change when someone opens the file in a different viewer. Flattening a PDF merges these layers into the page so that the document looks the same everywhere and cannot be edited by accident.
This free online tool to flatten a PDF offers two methods. Form fields only flattens the interactive form while keeping selectable text, links and vector graphics. Everything to images redraws every page as a picture, which flattens comments, stamps, annotations and layers as well. It shows how many fields and annotations it found, shows before and after previews, and runs in your browser, so your file is never uploaded.
How to flatten a PDF
- Choose your PDF. The tool counts pages, form fields and annotations and shows a preview of page 1.
- Pick a method. Form fields only for a filled form; Everything to images for a full lock.
- For the image method, set resolution and quality. 150 dpi at balanced quality suits most documents.
- Click Flatten and download PDF. A progress bar shows each page.
- Check the result. The After preview shows page 1, and the stats show the new size. Open the file and scroll through it before you send it.
Form flatten or image flatten: which one?
| Question | Form fields only | Everything to images |
|---|---|---|
| Keeps text selectable and searchable | Yes | No |
| Flattens form fields | Yes | Yes |
| Flattens comments and stamps | No, they stay | Yes |
| Keeps links | Yes | No |
| File size | About the same | Often larger, depends on dpi |
| Quality loss | None | Pages are rasterized at the chosen dpi |
| Best for | Filled forms, applications, tax forms | Final copies with markups, locked deliverables |
Why flatten a PDF?
- Consistent appearance. Some viewers hide typed form values or show different fonts. A flattened copy looks the same on every device.
- Prevent accidental edits. Recipients cannot change the answers in a flattened form.
- Make comments permanent. Review marks become part of the page so they are not lost when a viewer ignores annotations.
- Printing. Printers and print services sometimes ignore form fields. Flattened files print what you see.
- Archiving and submission. Many portals ask for a flattened PDF so that nothing can change after submission.
Flattening is not redaction
Flattening makes content permanent. It does not hide it. If you typed a number into a form and flatten the PDF, the number is still on the page. With the form-only method it is still in the file as text. Even with the image method, anyone who opens the file can read what is on the page. If you must remove sensitive information, use a proper redaction tool that removes the underlying content, then check the result. Also remember that any change to a file breaks an existing digital signature. Flatten first, then sign.
Choosing resolution and quality
In the image method each page is drawn to a bitmap and saved as a JPEG. The resolution, measured in dots per inch, decides how sharp the page is and how large the file becomes. 100 dpi is fine for reading on screen and keeps files small. 150 dpi is a good default. 200 to 300 dpi suits fine print, drawings and documents that will be printed at full size. The quality setting controls the JPEG compression: Small file is fine for plain text pages, while High is better for photos and scans. Large pages, such as posters, are limited so that browser memory is not exceeded.
Troubleshooting
- Form looks empty after flattening. Switch to the image method, which draws what a viewer shows.
- File became much larger. Lower the resolution or choose Small file quality.
- Text is blurry. Raise the resolution to 200 or 300 dpi.
- I need searchable text. Use the form-only method, or run OCR on the result in another tool.
- Password message. Unlock the PDF in the program that created it, then try again.
What this tool does not do
It does not redact, sign, compress deliberately, add OCR or repair damaged PDFs. Form-only flattening does not flatten comments, and the image method cannot keep selectable text. Very unusual forms, such as those using JavaScript to calculate fields, may need a check after flattening.
Flattening in common workflows
Job applications and official forms. Fill in the form in your PDF viewer, flatten it with the form method, and upload the flattened file. This avoids portals that drop typed values or show an empty form. Contracts and agreements. After all parties have filled in and reviewed the fields, flatten the file to stop anyone from changing an answer by accident, then add signatures. Reviewed documents. When reviewers have left highlights, sticky notes and stamps, use the image method to make the markup part of the page, for example for an archive copy or a printout. Print shops. Print services sometimes ignore annotations or substitute fonts in form fields. A flattened file prints what you see on screen.
Remember the order of operations. Flatten after you finish editing and before you sign, because both changes alter the file and a digital signature is invalidated by any later change. Keep an unflattened copy for the future in case a field needs to be corrected.
Flatten, print to PDF, redact or password-protect?
| Goal | Use | Why |
|---|---|---|
| Lock a filled form | Flatten form fields | Keeps text searchable and the file small |
| Make markup permanent | Flatten everything to images | Merges comments, stamps and layers into the page |
| Remove information for good | A proper redaction tool | Flattening does not delete what is on the page |
| Stop opening or copying | Password protection in a PDF editor | Encryption is a different feature |
| Create a clean copy of a web page | Print to PDF from the browser | Produces a new file instead of changing an existing one |
Printing a PDF to a new PDF file from your operating system also flattens most content, but it usually drops bookmarks, links and the text layer quality depends on the printer driver. The flatten tool gives you a controlled choice between keeping text and converting pages to images, and shows you a before and after preview so that you can see the effect.
If you are flattening a file for long-term archiving, consider that the image method discards the text layer. Some archives require searchable text, in which case the form method is the better choice, or you can run OCR on the flattened result in another program.
Privacy and how it works
Form flattening uses an open-source library to update field appearances and merge them into the page content. The image method renders each page on a canvas in your browser and builds a new PDF from the pictures. Your file is not uploaded, stored or logged. The libraries are fetched from a public CDN on first use, so you need to be online at that moment.
Related free tools
Use these free online tools together with this one:
- Sign a document with the PDF signer.
- Join documents into one file with the merge PDF tool.
- Remove a DRAFT stamp you added yourself with the PDF watermark remover.
- Check that a file has not changed with the hash generator.
- Create an invoice with the invoice generator.
- Reduce the size of pictures with the image compressor.
Frequently asked questions
What does it mean to flatten a PDF?
Flattening merges layers such as form fields, comments, stamps and annotations into the page so they can no longer be edited, moved or turned off. The page looks the same but is fixed.
How do I flatten a PDF form for free?
Choose your PDF, keep the method Form fields only, and click Flatten and download PDF. Filled-in fields become plain text and checkmarks that stay in place.
Is my PDF uploaded?
No. Flattening happens in your browser. The PDF libraries are loaded from a public CDN on first use, but your document is not sent anywhere.
What is the difference between the two methods?
Form fields only keeps your text, links and vector graphics and just locks the form. Everything to images draws each page as a picture, which also flattens comments, highlights, stamps and layers, but text can no longer be selected or searched.
Which method should I choose?
Use Form fields only for filled forms where you want to keep text searchable and the file small. Use Everything to images when you must also lock annotations or you need a file that cannot be edited with text tools.
Will flattening make the file bigger or smaller?
Form-only flattening usually changes the size very little. The image method can make a text PDF larger, because pictures take more space than text. Lower the resolution or quality to shrink it.
Can I undo flattening?
No. Keep your original. After flattening, the fields cannot be edited again unless you recreate them.
Does flattening remove the information typed into the form?
No. It makes the information permanent and visible on the page. To hide sensitive data you need real redaction, not flattening.
Does flattening remove a digital signature?
Any change to a PDF breaks an existing digital signature. Flatten and then sign again if you need a valid signature.
Why print or flatten a form before sending it?
Some viewers display form fields differently, drop typed values or let the recipient change them. A flattened copy looks the same everywhere and cannot be edited by mistake.
Does it flatten comments, highlights and sticky notes?
The Everything to images method does. The Form fields only method keeps them as they are.
Will links still work after flattening?
After form-only flattening, links usually stay. After the image method, links are lost because each page becomes a picture.
What resolution should I choose?
150 dpi is a good balance for screen reading and ordinary printing. Use 200 or 300 dpi for fine print or detailed drawings, and 100 dpi for the smallest files.
Why does my flattened form look empty?
Some PDFs store field values without a visible appearance. Try the Everything to images method, which renders what a viewer displays.
Does it work on a password-protected PDF?
Not directly. Remove the password first, or print the PDF to a new file, and try again.
Is there a page limit?
No fixed limit. The image method uses memory per page, so very large PDFs can be slow on older phones and laptops.
What can I print or save?
Flatten and download PDF saves the result. Print / save summary prints the settings, counts and before and after previews, and Copy summary copies them as text.
Sources and further reading
- Adobe / ISO 32000-1:2008, Section 12.5 Annotations and Section 12.7 Interactive Forms, for how fields and annotations are stored in a PDF.
- pdf-lib documentation, PDFForm.flatten, for merging form fields into page content.
- Mozilla PDF.js documentation, annotation rendering modes, for drawing pages with their annotations.
- Adobe, About PDF forms and flattening, general guidance on making form entries permanent.
Sources were consulted in October 2026. Standards and rules can change, so always check the official page for your situation.