How to Secure a Digitally Signed and Encrypted PDF
Question details
The user needs to add a digital signature to a multipage PDF document and protect it against editing, and wants to know if signing and encryption can be used together.
- Product
- Adobe Acrobat Pro 2017
- Device & OS
- not provided
- Scenario
- Securing a multipage PDF document by using both digital signatures for authenticity and encryption for restricting unauthorized edits.
- Observed behavior
- The goal is to achieve a dual-layered security setup where the PDF is both authenticated with a reliable signature and encrypted against unauthorized modifications.
Ensure you have your digital certificate ready and decide whether you need to restrict editing (permissions password) or restrict opening (document open password) before applying the signature.
Apply Permissions Password Followed by a Digital Signature
Use this method to restrict unauthorized edits while ensuring the document's integrity through a certificate-based signature.
A digital signature proves the document hasn't been altered after signing, while encryption (permissions password) actively prevents users from making changes. It is generally best to apply the security restrictions first, and then sign the document.
Test the workflow with your intended recipients to ensure they can view the document and validate the signature without issues. Avoid relying solely on self-signed certificates if identity verification is strictly required by third parties.
Open your PDF in Adobe Acrobat Pro 2017 and go to Tools > Protect. Select 'Advanced Options' and choose 'Encrypt with Password'.
Check 'Restrict editing and printing of the document' and enter a secure permissions password. Click OK and save the document.
Go to Tools > Certificates and click 'Digitally Sign' from the top toolbar.
Click and drag a rectangle to place your signature on the page. Select your digital ID from the prompt, and click 'Sign' to save the finalized secure PDF.
Easily Sign and Encrypt PDFs with WPS Office
WPS PDF offers a streamlined, user-friendly way to add digital signatures and apply robust password protection to your documents without needing expensive software.
- 1. Open PDF in WPS: Launch WPS Office and open your multipage PDF document.
- 2. Encrypt the File: Go to the 'Protect' tab and select 'Encrypt' to set a permissions password that restricts edits.
- 3. Add Signature: Navigate to the 'Protect' tab, click on 'Sign', and choose 'Add Signature' or use a digital certificate to authenticate the file.
- 4. Save Changes: Save the document to lock in both the encryption restrictions and the digital signature.
Frequently Asked Questions
Can I encrypt a PDF after I have digitally signed it?
It is highly recommended to apply password encryption before adding a digital signature. Encrypting a document after it has been signed will alter the file data, which instantly invalidates the existing digital signature.
Why does my digital signature show as invalid when the recipient opens the PDF?
This usually happens if the recipient's PDF reader does not trust the certificate used to sign the document (which is common with self-signed certificates) or if the document was modified or compressed after the signature was applied.
Is a digital signature better than password protection for preventing edits?
They serve different purposes. Password protection attempts to block edits outright via software restrictions, while a digital signature provides document integrity by proving whether the file has been tampered with. Combining both offers the best security.
