How to Verify a Digital Signature in a PDF?

27 May 2026

Digital signatures are your personal asset that is extremely confidential and non-negotiable to have for key tasks. That’s why it is kept surveilled. So, when you try to open its PDF and it shows an irritating question mark (?) on the signature lock, understand that it wants to check the validity. The question mark symbolizes "validity unknown."

So here, you don't need to panic. That red sign is not saying that your document is fake. It just means that your PDF reader is acting like a janitor or security guard who does not recognize the person who just signed in. 

For sure, it’s a problem. Now, your computer needs the trust signal to open it. So, these steps can help you to remove that confusion and see the red question mark changing into a green checkmark, which means “Valid Signature." Let’s dive into these steps to verify your digital signature in a PDF by using the free Adobe Acrobat Reader.

The 5-Step Secret to a Green Checkmark

Make sure you open your document inside the official Adobe Acrobat Reader software on a laptop or PC (this doesn't work well on basic web browsers like Google Chrome).

Step 1: Click the question mark

Open the PDF file and mouse over the digital signature block. It’s mostly located at the bottom of the page. Now, move your mouse on the box that shows the red flag, or the "Validity Unknown” message. As you click, a small dialog box will pop up, namely “Signature Validation Status." 

Step 2: Open the Properties

Closely watch that popped-up box and click on the button that consists of the "Signature Properties." As you click, a larger menu with multiple technical details will flash. 

Step 3: Show the Signer's Certificate

Now, search for a button labeled “Show Signer’s Certificate." You can easily find it under the summary or “signer” tab. Once found, click it. This action will click open the digital identity card or DSC of the person or government authority who signed your online document. 

Step 4: Add to Trusted Certificates

Now, this is where some crucial things will go on. 

1. Take a look at the top tabs in this new window. Now you see the “Trust” tab, where you should click.
2. Now, you need to add the digital certificate. Click that button (as aforesaid) that says "Add to Trusted Certificates." Or you may add to trusted identities.
3. Thereafter, a small alert box might pop up to ask if you want to proceed with the action. Click "Ok."
4. Next up will be a window showing a bunch of empty checkboxes. Tick all the boxes that you see, especially the one saying “Use this certificate as a trusted root." Once done, check everything. If all things are fine, click ok.

Step 5: Validate!

Thereafter, click off the smaller pop-up windows by tapping on "OK" until the system directs you to the main document page. The final step is to click the button that says “Validate Signature."

And that’s it! The red question mark will transform into a green check mark.

What Does a Valid Signature Tell You?

As Adobe learns that the certificate is authentic, it simultaneously does these things in the backend:

1. Authenticity Audit: It proves the real identity of the signing authority. For example, a real official from the MCA or ROC or an enterprise authority like eMudhra can send his attested document digitally.
2. No Tampering: The digital signature verification confirms that nobody has changed even a single letter or number in the PDF since it was signed. If a hacker tries to tamper with it, the signature will automatically show that its authority has been compromised.

Conclusion

The trustworthiness of the digital document depends on the intact and untampered signature. You can check it by following these steps: Click "?" ➔ Signature Properties ➔ Show Signer's Certificate ➔ Trust Tab ➔ Add to Trusted Certificates ➔ Check All Boxes ➔ Validate. Once followed, these steps will successfully let you see a real digital signature that you can trust