Flatten a PDF form and its annotations

How it works

Tap or click the box to select the PDF form you filled in. A typical case: you completed a fillable application, rental or insurance form with your name, address and a few ticked boxes. Sent as it is, the recipient's app may show the fields empty, or anyone could change the values. Select the file and press "Flatten": each field's value is written onto the page itself and the field is removed. The downloaded -flat.pdf looks the same in every app and on every printer, and the values can no longer be clicked and changed. The "What to flatten" option also bakes comments, highlights and drawn signatures into the page; choose form fields only if the comments should stay editable. The result line tells you how many fields and annotations were flattened and, if any annotation had no appearance to draw, how many were left in place. Links keep working. Flattening cannot be undone, so keep the fillable original.

This tool is also known as flatten pdf, flatten pdf form, make fillable pdf not editable, flatten pdf annotations, lock pdf form fields, flatten pdf online.

What is PDF form field (AcroForm)?

AcroForm is the PDF system for fillable forms. Text boxes, check boxes, radio buttons and drop-down lists sit on top of the page as separate objects, and the value you type is stored inside the field. How the field looks on screen is decided by a small drawing called an appearance stream. Some apps save the value without updating that drawing; if the recipient's reader does not redraw it, the field looks empty. Before flattening, this tool redraws missing appearances with a font that covers accented letters, then writes them onto the page.

What is PDF annotation (comment, highlight, stamp)?

The PDF standard calls comments, highlights, stamps, freehand drawings and text boxes annotations. They are not part of the page content but a separate layer on top of it: some printer drivers and older apps skip them, some readers hide them, and anyone can move or delete them. Flattening copies each annotation's appearance into the page content and deletes the annotation, so a highlight or a drawn signature becomes part of the page. Links are technically annotations too, but they are kept so they stay clickable.

What is the difference between flattening a PDF and converting it to images?

Flattening only merges form fields and annotations into the page; everything else stays as it was. Text remains selectable and searchable, the file size barely changes and the lettering stays sharp at any zoom. Converting the PDF to images turns every page into a single picture: forms and comments end up in the picture too, but no text can be selected any more, the file grows and letters blur when you zoom in. If you only need the values to be uneditable, flattening is enough; if no text at all should be extractable, the image route is the one.

What changes when you flatten, and what stays?

Changes: form fields are removed and their values become part of the page drawing. The text in a box, the tick in a check box and the selected entry of a drop-down list sit on the page like printed text; they can no longer be clicked, deleted or tabbed through. With everything selected, comments, highlights, stamps and pen-drawn signatures are merged the same way, and the pop-up windows of sticky notes are removed.

Stays: the page text, images, fonts, bookmarks and links. Fields and annotations marked as hidden are removed without being drawn, because readers were not showing them anyway. An annotation without an appearance drawing (some sticky notes from older programs) cannot be drawn; the tool leaves it in place and reports how many there were.

When to flatten, and what to watch out for

Flatten a completed form before you email it or upload it to a portal: whatever app the recipient uses, the values show, and nobody can change them later. Do not flatten a form that other people still have to fill in; they would find no fields left. Flattening is permanent, so keep the fillable original.

Do not flatten a PDF that carries a digital signature. Any change to a signed file breaks the signature check, and if the signature field itself is flattened the signature data is gone. Flatten first, sign last. A picture of a handwritten signature is not a digital signature in this sense and can be flattened safely.

Frequently asked questions

How do I make a fillable PDF non-editable?

Fill in the form and save it, then select it on this page and press "Flatten". The downloaded file has no fields; the values are part of the page. Printing to "Save as PDF" in Chrome gives a similar result, but values whose appearance was never drawn can print empty and links are lost.

Why do my filled-in answers show up blank for the recipient?

The app you filled the form in saved the values but not their appearance, and the recipient's reader does not redraw fields by itself. This tool redraws missing appearances before flattening, with a font that covers accented letters, so the values show in every reader.

Can a flattened PDF be unflattened?

No. The fields are deleted and the values become part of the page drawing. Keep the fillable original and, if something needs changing, edit the original and flatten it again. The text stays selectable, so values in a flattened form can still be copied.

Is my file uploaded anywhere?

No. Reading the fields, drawing their appearance and rewriting the file all happen in your browser; the personal details in your form never leave your device. Once the page has loaded, the tool works even offline.