Why You Cannot Sign a PDF with an Existing Digital Signature
Question details
The user is unable to add their own digital signature to a PDF document that already contains a certified digital signature.
- Product
- Device & OS
- not provided
- Scenario
- Attempting to co-sign or add an additional signature to a PDF file that has already been digitally signed by another party.
- Observed behavior
- The signature feature is disabled or grayed out, and the document is locked or restricts further changes, preventing the addition of a new signature.
Before attempting to force a signature, verify whether the document contains specific, pre-assigned signature fields designated for your name.
Use an Available Pre-Assigned Signature Field
When a PDF is certified, general signing tools are often disabled. You must use a specifically assigned signature field if one was provided by the author.
Often, the creator of a certified PDF will disable general editing and signature features to protect the document's integrity. However, they may leave specific empty signature fields active for subsequent signers.
Scroll through the PDF document to locate any empty signature boxes.
Click directly on the designated signature field. If permitted, a prompt will appear allowing you to apply your digital certificate.
Follow the on-screen instructions to insert your digital ID and save the newly signed document.
Request an Unlocked Copy from the Sender
If the original signer locked the document upon certification, it is mathematically impossible to add another signature without invalidating the first.
Manage PDF Signatures and Security with WPS Office
WPS Office provides a comprehensive suite of PDF tools, allowing you to easily view document permissions, insert digital signatures, and manage secure files without any hassle.
- 1. Open the PDF: Launch WPS Office and open the PDF document you need to sign.
- 2. Navigate to the Protect tab: Click on the 'Protect' tab located in the top ribbon menu to access security features.
- 3. Check permissions: Click 'Document Properties' and view the 'Security' tab to ensure signing is allowed.
- 4. Add your signature: Click 'Sign Document' or click directly on an available signature field to apply your digital signature.
Frequently Asked Questions
Why does a certified digital signature lock a PDF?
A certified signature guarantees the document's integrity. The author can choose to restrict all changes, including the addition of new signatures, to ensure the document remains exactly as it was when they signed it.
How can I check if my PDF has editing and signing restrictions?
Open the PDF in your reader, navigate to 'Document Properties' (usually under the File menu), and click the 'Security' tab. This section will list whether actions like signing, editing, and printing are allowed or restricted.
Can multiple people sign a single PDF digitally?
Yes, multiple people can sign a PDF, provided the first person to sign does not select the 'Lock document after signing' option. If left unlocked, subsequent users can add their signatures to the existing file.
Can I remove the existing digital signature to unlock the PDF?
No, you cannot remove someone else's digital signature. Only the person who originally placed the signature can clear it, and they must use the same digital ID they used to sign it.
