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The reorder tool warns that my PDF has a digital signature. What does that mean, and should I carry on?

It means the tool found a digital signature in your file, and saving it in a new order will change its bytes so the signature no longer validates. If the signature matters, as with a signed contract or an official certificate, stop: keep the original and ask the issuer for a corrected file. Carry on only if a copy for reading is all you need.

Published · 3 min read

How a digital signature works, briefly

A digital signature is not a picture of a signature on the page. It is a fingerprint of the file's data as it was at the moment of signing, sealed with the signer's certificate. When someone opens the file, the PDF reader recomputes the fingerprint and compares. Any change after signing, even swapping two pages without touching a single word, makes the fingerprints differ, and the reader reports the signature as invalid or the document as modified after signing.

The reorder tool rewrites the file in the new order, which necessarily changes its data. So it looks for signature markers when you open the file and warns you up front, rather than after you have sent the file to someone.

Stop in these cases

  • A contract signed by both parties through an e-signature service.
  • A certificate or official letter from an organisation that relies on signature verification.
  • A document you will submit to a bank, a government body or in a dispute, where someone may check the signature.

If the page order in such a file is wrong, ask whoever signed it to issue a corrected version and sign it again. A signed file in an awkward order beats a tidy file with a signature that fails. This is not legal advice; if it matters, ask the receiving party what they accept.

When carrying on is fine

  • You need an internal copy for reading or printing, arranged in a way that suits your team.
  • The signature is old or irrelevant to your purpose, such as a supplier catalog that signs every file it sends out automatically.
  • You keep the signed original filed safely and use the reordered copy only for day-to-day work.

If you decide to continue

  1. Open Reorder PDF pages, choose the file and read the warning.
  2. Arrange the pages as you need and check the “New order” line.
  3. Press “Download in new order”. The output has reordered in its name, so it is easy to tell apart from the signed original.
  4. Do not delete the original, and never send the reordered copy as if it were the signed document.

Common questions

Does reordering damage the signature on my original?

No. The tool creates a new file and leaves the original on your device untouched, so its signature stays valid.

Is there any tool that reorders pages and keeps the signature valid?

Changing page order is a change to the document, and a digital signature exists to reveal changes made after signing, so the right route is a new version signed by its owner.