Guide

How to make a PDF form uneditable

Open Flatten PDF, add your filled-in form, keep Form fields ticked and press Flatten PDF. The typed text, ticks and choices become part of the page, and the fillable boxes are gone. It runs in your browser, so the form is not uploaded.

By Akash Gupta · · Updated

Open Flatten PDF

Step by step

  1. Open Flatten PDF. Go to the Flatten PDF page on PlumPDF. No sign-up and nothing to install.
  2. Add your filled-in form. Drop the PDF on the box, or click to browse. You can add up to 50 files of 100 MB each.
  3. Choose what to flatten. Pick Form fields, comments and markup, or both. Links always stay clickable.
  4. Flatten and download. Press Flatten PDF. The result says how many fields and annotations were flattened. The file is saved with -flat added to its name.

Why is a filled form still editable?

In a PDF form, every box is a live field sitting on top of the page. Anyone with the file can click into a field and retype it, untick a box or clear a choice. Comments, highlights and stamps are similar: they are separate objects that a reader can hide or delete.

Flattening draws each of them into the page itself and removes the separate object. What you see stays the same, but it is now ordinary page content.

When should I flatten a form?

Flattening makes sense once the content is final:

  • Before sending a completed application or order form.
  • After signing, so the signed copy cannot be quietly changed in a field.
  • Before sharing a marked-up document, so every reader sees the same comments.
  • When a reader shows form text differently from another and you want one fixed look.

What does flattening not do?

It is not a lock. A flattened PDF can still be changed with a full PDF editor, because the content is simply no longer a form. To stop other people opening the file at all, add a password with Protect PDF.

A comment with no picture of its own, such as a sticky note saved by some programs, has nothing to draw, so PlumPDF leaves it as it was. The result tells you how many were left.

Why keep a copy first?

Flattening cannot be undone, since the fields no longer exist. Keep the fillable original in case you need to correct something later. Your original is not changed, and you download a separate flattened file.

Questions

Will my typed text still show?

Yes. Form fields are brought up to date first, so what you typed appears in the flattened page even if the form relied on the reader to draw it.

Do links still work?

Yes. Links have nothing to draw, so they are left in place and stay clickable.

Can I flatten only the comments and keep the form fillable?

Yes. Choose comments and markup only, and leave Form fields unticked.

Does flattening remove hidden data from the file?

Not on its own. For author names, earlier versions and other hidden data, use PDF Privacy Check.

Can I flatten many forms at once?

Yes. Add up to 50 PDFs of up to 100 MB each and flatten them together. Each result says how many fields and annotations were flattened, and you can download the files one by one or as a zip. This helps when you have a whole batch of completed forms to send.

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