Flatten PDF: what it is and what it is for

In 30 seconds

Flattening merges annotations, visual signatures and form fields into the page so they cannot be moved or edited.
In Rayo PDF GO every page becomes an image, so the text can no longer be selected.
It is not encryption: the file opens the same way; the only change is that the content is no longer editable.
It cannot be undone, so it is best to keep the original.

1What does flattening a PDF mean and what is it for?

A PDF can store certain elements as layers separate from the base content: comments and highlights, drawings, signatures placed on top, fillable form fields, watermarks. As long as they are separate layers, they can be moved, edited or deleted. Flattening the PDF means merging everything into the page itself, so that you can no longer touch each piece separately.

It is used to lock in a final result: a form that has already been filled in, a signed document, a contract with review notes you want to freeze, or a file you are about to send and do not want modified by accident. It also helps the document look the same in any viewer, because it no longer depends on how each one interprets the annotations.

2How does flattening work under the hood?

There are two ways to do it. One is to draw the annotations and fields into the page content and discard the original objects, keeping the text as text. The other, more drastic, is to generate an image of each page as it looks and build a new PDF from those images.

In Rayo PDF GO the result is of this second kind: each page becomes an image. It guarantees that what you see is exactly what gets locked in, but it has a cost: the text stops being text and can no longer be selected, searched or copied. That is why the resulting file can weigh more and look slightly less sharp when you zoom in a lot.

3What gets flattened, and what variants exist?

What gets flattened is mainly annotations (notes, highlights, stamps, drawings), form fields with their values, visual signatures and watermarks added as objects. In some programs, optional layers and complex transparency are flattened as well.

Some programs let you choose what to flatten: only the forms, only the annotations, or all the content. Rayo PDF GO offers a simple, complete flatten, designed for people who want to close a document without complications. If you need to keep the text selectable, you will have to decide whether that approach is the right one.

4When should you flatten, and when not?

Flatten before sending a filled-in form to someone who should not change it, after placing a visual signature so it does not shift, after adding a watermark you do not want to be easy to remove, or when a document looks different in two viewers because of the annotations.

Do not flatten if you still need to edit the document, if the recipient needs to fill in the form, if you need to keep the text for searching or copying, or if the file carries a certificate-based digital signature, because any modification invalidates it. Always flatten a copy, never your only original.

5Common mistakes and myths about flattening

The most widespread mistake is confusing flattening with encryption. A flattened PDF opens without a password and its content is still visible; the only thing that changes is that it can no longer be edited easily. If what you want is confidentiality, you need Protect PDF. It is not the same as redacting either: to truly remove a piece of sensitive data, the right tool is Redact PDF.

Another myth is that flattening is reversible or that there is a button to undo it. There isn't: what is merged stays merged. People also believe a flattened PDF is impossible to modify; with the right tools the resulting image can be edited, so it is not a guarantee of integrity.

6Common problems and how to fix them

If you can no longer search for text after flattening, that is expected: apply OCR to the result to get a text layer back, knowing it may contain recognition errors. If the file is heavier, use Compress PDF. If the text looks slightly blurry when you zoom in, keep in mind it is now an image and not vector-based; it is best to flatten only at the end.

If you need to edit again, you will have to go back to the original you saved beforehand. And if a form got locked in with a wrong value, the only way out is to redo it from the unflattened copy.

7Flattening and working in Rayo PDF GO

Flatten PDF works on your device and the document is not uploaded to any server, which makes it a good fit for forms with personal data. It is usually the last step in a workflow: Edit PDF to fill in or annotate, Sign PDF to place the signature, Watermark if needed and, finally, Flatten PDF to lock everything in.

Afterward, if you want to control access, add a password with Protect PDF. If you need to get searchable text back, use OCR. And always keep the editable original: it is the only way to go back.

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Frequently asked questions

Can flattening a PDF be undone?

No. That is why you should keep the editable original and always flatten a copy.

Why can't I select text after flattening?

Because in Rayo PDF GO each page is converted to an image, and the text no longer exists as text. You can get it back with OCR.

Is flattening a PDF the same as encrypting it?

No. Flattening prevents editing, but the file opens without a password. To limit access, you have to protect the PDF with a password.

Does flattening remove sensitive information?

That is not its purpose. To delete data permanently, use a permanent redaction tool.

What happens to a digital signature when I flatten?

It is invalidated, because the document changes. If you need both, flatten first and sign with a certificate at the end.

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