A digital signature on a PDF is only useful if you actually check it. Whether you've received a signed contract, an Aadhaar e-PDF, a GST certificate, or an offer letter, verifying the signature confirms the document is genuine and hasn't been tampered with. This guide shows you the fastest way to do it, online, with nothing to install, and explains what the results mean.
The fastest way: check a PDF signature online
The simplest method needs no software at all. Open our PDF signature validator, drag your signed PDF onto the page, and read the report. In a second or two you'll see an overall status (Valid, Warning, or Invalid) plus a breakdown of every signature in the file: whether the document is unchanged, whether the signature verifies cryptographically, the signer's certificate details, the trust chain, and any timestamp.
Because the validation runs entirely inside your browser, the document is never uploaded to a server. That matters when the file is sensitive, and most signed documents are. You can confirm there's no upload yourself by opening your browser's network inspector while you validate.
- Open the validator: go to the homepage.
- Drop your PDF: drag and drop, or click to choose the file.
- Read the report: overall status, signer, certificate, trust chain, and warnings.
- Download proof if needed: export the result as a PDF or JSON report.
What the results mean
A Valid result means the signature is cryptographically intact and the document hasn't changed since it was signed and, ideally, that the signer's certificate chains to a trusted authority. A Warning usually means the signature math is fine but something needs your attention: the certificate's trust chain couldn't be fully established, the certificate has expired, or content was added after signing. An Invalid result means the signature failed or the document was modified after signing: that's the genuine red flag worth investigating. For more on the warning case, read why a PDF signature shows as not valid.
Reading the certificate details
The report shows the signer's certificate so you can judge who actually signed the document. Useful fields include the Common Name and Organization (the signer's identity), the Issuer (the authority that issued the certificate), the validity dates, and the signature and hash algorithms used (for example RSA with SHA-256). If the signer is a government body, for instance UIDAI on an Aadhaar PDF, that will be clear from these details.
How to verify a PDF signature in Adobe Reader
You can also check a signature in Adobe Acrobat Reader. Open the PDF and click the signature panel (or the banner across the top). Adobe will show whether the signature is valid and the document unchanged. The catch: Adobe only trusts certificates on its own approved trust list and your operating system's store, so signatures from many government authorities, including UIDAI, show a yellow question mark ("validity unknown") by default. That doesn't mean the signature is fake; it means Adobe doesn't recognise the issuing root. You can fix it by importing the relevant root certificate into Adobe's trusted identities, a one-time setup per computer. Our online validator avoids this entirely by bundling the relevant government root.
Checking multiple signatures
PDFs can carry more than one signature, for example a form signed first by an applicant and then countersigned by an approving officer. A good validator reports each signature separately and tells you whether the most recent one still covers the entire document. Our tool lists every signature with its own status so you can see the full picture, not just the last one.
Special case: Aadhaar and Indian government PDFs
Aadhaar e-PDFs are signed by UIDAI through licensed Indian Certifying Authorities. They very commonly show a question mark in Adobe, which worries people unnecessarily. Our Aadhaar signature validator detects the UIDAI signature, labels the signing authority, and, because it trusts the official CCA India root, reports the signature as genuinely valid. If your Aadhaar is still password-protected, you can remove the password first.
Verify it yourself now
The quickest way to learn what a valid signature looks like is to try it. Open the PDF signature validator and check any signed PDF you have. If you'd like to see the full lifecycle, you can even sign a PDF yourself and then validate your own signature.