A fillable PDF keeps your answers in form fields that sit on top of the page. That is handy while you fill it in, but it causes trouble once you send it: the recipient can change the answers, some viewers and printers show the fields empty, and online portals sometimes reject forms that are still fillable. Flattening fixes this by drawing each field's value into the page itself, so what you see becomes ordinary page content.
This tool flattens form fields with pdf-lib, an open-source PDF library, right in your browser. The PDF never leaves your device, which matters for tax forms, applications and contracts full of personal details.
How to flatten a PDF
- Drop the PDF on the box at the top of this page, or click it and choose the file.
- Check the form fields found table. It lists each field's name, its type (text, checkbox, radio buttons, dropdown, list, signature), the current value and the page it is on. Empty fields are marked as empty.
- If the PDF also has comments or markup, a line under the table lists them, such as "Highlight x3 (page 2), Sticky note x1 (page 5)".
- Decide whether to tick Also flatten comments, highlights and stamps. Leave it off to flatten only the form, which keeps text selectable. Tick it to make everything part of the page, and pick 150, 200 or 300 DPI.
- Click Flatten. The result shows how many fields were flattened and the new file size.
- Download the file. It is named after your original with
-flattenedadded (or-flattened-imagewith the image option), and the original is not changed.
What flattening does
Each form field in a PDF has a value and an appearance, the little drawing a viewer shows for it. Flattening takes that appearance, draws it permanently onto the page, and removes the field. After flattening:
- Typed answers, ticked checkboxes, chosen radio buttons and dropdown values look exactly as they did, but they are part of the page.
- Nobody can click into a field and change the answer, because there are no fields left.
- Every viewer shows the values, including browsers, phone apps and print drivers that ignore form data.
- Text stays selectable and searchable when you flatten the form only, because the values are drawn as text.
To draw text fields, the tool regenerates their appearance from the stored value, using Helvetica at the field's font size. In most forms this matches what you saw. If a field holds characters Helvetica cannot draw, such as Arabic, Chinese or emoji, the tool falls back to the appearance saved in the file and tells you so.
How each field type flattens
| Field type | After flattening |
|---|---|
| Text | The typed value drawn as text, inside the field's box and at its font size |
| Checkbox | The tick or empty box exactly as the form drew it |
| Radio buttons | The chosen option shown as selected, the others empty |
| Dropdown and list | The selected value drawn as text; the other options are gone |
| Button | Its label or picture stays, but clicking it does nothing |
| Signature | A drawn signature stays visible; the digital signature data no longer validates |
Field borders and background colors that the form designer added are part of each field's appearance, so they stay on the page. A form with light blue field boxes keeps its light blue boxes, now as plain shapes.
Form fields versus comments
Comments, highlights, sticky notes, drawn shapes and stamps are a different kind of object called annotations. Flattening the form does not touch them, so they stay as editable comments. There is no reliable way to bake every annotation type into the page as vector content in a browser, so this tool offers the method that always works: drawing each page as an image.
| Flatten form only | Also flatten comments (image option) | |
|---|---|---|
| Form field values | Fixed into the page | Fixed into the page |
| Comments, highlights, stamps | Left as editable comments | Fixed into the page |
| Text selectable and searchable | Yes | No, pages become pictures |
| Links | Still work | Stop working |
| File size | Usually smaller than before | Usually larger, grows with DPI |
| Best for | Forms, applications, tax documents | Marked-up drafts, reviewed contracts, stamped copies |
Warning: with the image option, each page is redrawn as a picture at the DPI you choose. The text can no longer be selected, searched, copied or read aloud by a screen reader, and links stop working. Keep the original if you may need any of that later.
When you should flatten a PDF
- Before sending a completed form. W-9s, rental applications, vendor setup forms and onboarding packets should reach the other side exactly as you filled them in.
- When answers disappear in other apps. Some phone viewers, older printers and e-signature tools show a fillable form as blank or lose checkbox ticks. A flattened copy always shows the values.
- When a portal rejects the upload. Some government, bank and insurance portals refuse PDFs with active form fields. Flattening usually fixes it.
- Before merging. Combining several filled forms with Merge PDF can confuse fields that share a name, such as two forms that both have a field called "Name". Flatten each one first and the values stay put.
- Before sending a reviewed draft. If your comments and highlights should be seen but not edited, use the image option.
Worked examples
A filled vendor form
A wholesale supplier sends a 2-page vendor form with 6 fields: business name, email, a gift wrap checkbox, a size radio group, a shipping dropdown and a notes field on page 2. Drop it in and the table lists all 6 with their values and pages. Click Flatten 6 fields. The download shows the same answers, but clicking on them does nothing, and the file went from 12.9 KB to 8.9 KB because the field structure is gone.
A contract with review comments
A 9-page contract has 14 highlights and 3 sticky notes from your review, and the client should see them without being able to delete them. The table reports no form fields, and the comment line lists the highlights and notes. Tick the image option, keep 200 DPI and click Flatten into images. Each page becomes a 200 DPI picture with the highlights burned in. Expect the file to grow: each page is now a 1700 x 2200 pixel image, which typically adds tens to a few hundred kilobytes per page depending on how much is printed on it.
A form with a signature field
If the table includes a signature field, the tool warns you. Flattening changes the file, so an existing digital signature will no longer validate. Flatten a copy for viewing or printing and keep the signed original as your record. To add a visible signature to a PDF, use Sign PDF, then flatten the copy you send.
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Choosing a DPI for the image option
| DPI | US Letter page in pixels | Use it when |
|---|---|---|
| 150 | 1275 x 1650 | The file is only read on screen and must stay small, such as an email attachment |
| 200 | 1700 x 2200 | Default. Sharp on screen and fine for office printing |
| 300 | 2550 x 3300 | The document will be printed and must look crisp, or has very small print |
Check the flattened file before you send it
- Open the download in a different viewer from the one you filled it in with, for example your browser if you used Acrobat Reader. The answers should all be there.
- Click on a few answers. Nothing should happen, which confirms the fields are gone.
- Press Ctrl+F (Cmd+F on Mac) and search for a word you typed into a field. With the form-only option it is found, because it is real text. With the image option it is not.
- Print one page if the form is going on paper, to check that small checkboxes and tiny text are readable.
Other ways to flatten a PDF
- Print to PDF: printing a filled form to Microsoft Print to PDF on Windows or choosing Save as PDF in the Mac print dialog usually flattens it, because printing only keeps what is drawn. The catch is that some apps leave form values out of the printout, and page sizes or margins can shift.
- Adobe Acrobat: the paid Acrobat apps can print a form to the Adobe PDF printer, which gives the same result as other print to PDF methods, with the same caveats.
- Scan or photograph a printout: it works in a pinch, but the result is a blurry image with no searchable text and a much larger file.
The tool on this page avoids the print step, so page sizes stay exact and, with the form-only option, text remains searchable. It also shows you every field and value before you flatten, which a print dialog never does, so you can spot a field you forgot to fill in while you can still fix it.
Troubleshooting
- No form fields were found, but the PDF looks fillable. The "fields" may be comments or text boxes added with a markup tool. Use the image option. A small number of forms are XFA forms made with Adobe LiveCycle or AEM; the tool removes the XFA layer and flattens any standard fields, and if pages come out empty, print the form to PDF from Adobe Acrobat Reader first.
- A field's font looks different after flattening. Text fields are redrawn in Helvetica. If the exact font matters, use the image option, which draws the fields the way your PDF viewer shows them.
- The PDF will not open. If it has a password or editing restrictions, remove them first with Unlock PDF, which needs the password.
- The image version is too large. Choose 150 DPI, or run the result through Compress PDF.
- Flattening failed with an error. The form structure in the file is damaged. The image option works with almost any PDF, because it only needs to draw the pages.
What flattening does not do
Flattening is not security. A flattened PDF can still be edited by anyone with a PDF editor, the same way any page content can. It stops casual changes to form answers, not deliberate tampering. If the recipient must be able to prove the document was not altered, use a proper digital signature service. Flattening also does not hide information: anything visible before is still visible after, so remove private details first, for example with Delete PDF Pages for whole pages.
Privacy and limits
The tool is free, with no daily limit, no account and no watermark. Your PDF is read, flattened and saved inside your browser and never uploaded. The image option draws every page in memory, so very long documents at 300 DPI are more reliable on a computer than on a phone.