Validate Digital Signature in PDF Online | Confirm Document Integrity
A digital signature is only as good as its underlying security—and most people have no way to check it. You receive a signed contract, an executed invoice, or a countersigned agreement. The signature looks legitimate. The document appears unchanged. But how do you actually know? How do you know the signature belongs to who it claims to belong to? How do you know the terms weren't quietly amended after the signing event, in the seconds between the signature being applied and the file landing in your inbox?
Cryptographic certainty. Instant results. Legally sound.
Get cryptographic proof instantly. Validate a digital signature in a PDF online to authenticate the signer's identity and confirm PDF document integrity with mathematical precision. Our engine reads the digital certificate embedded in the signature and compares the document's current hash against its state at the exact moment of signing. Any alteration—a changed word, a modified number, even a deleted space—breaks the hash and triggers an immediate tamper warning. Ensure your legally binding documents are 100% tamper-free before you act on them.
This is what it means to truly validate an e-signature and confirm PDF document integrity.
How to Verify e-Sign and Check PDF Integrity
Step 1: Upload Your Signed Document
Drop your electronically signed document into our secure verifier. Contracts, invoices, HR agreements, court filings, real estate closing documents, NDAs—any PDF carrying a digital or electronic signature that you need to authenticate. Your file is encrypted immediately on upload. The verification process is fully automated and completely private.
Step 2: Cryptographic Analysis
Our engine reads the digital certificate (PKI — Public Key Infrastructure) embedded within the signature and performs a two-part verification. First, it authenticates the certificate itself: who issued it, whether it belongs to the named signer, and whether it was valid and trusted at the time of signing. Second, it computes the document's current cryptographic hash and compares it against the hash recorded at the exact moment of signing. These two checks together answer the two fundamental questions of digital signature validation: Is this signature authentic? Has this document been changed?
Step 3: View Your Validation Report
Instantly receive a clear, definitive validation report with one of three results. Valid: the signature is authentic, the certificate is trusted, and the document is completely unchanged since signing. Invalid: the certificate is untrusted, expired, or the signature cannot be authenticated to the claimed signer. Modified/Tampered: the signature was once valid, but the document has been altered after signing—the hash no longer matches. Each result comes with a detailed breakdown so you know exactly what was checked and exactly what was found.
Upload, analyze, verify. Cryptographic certainty delivered in seconds, on documents that require nothing less.
Why You Must Validate Digital Signatures — The Risks of Taking Them on Faith
🔍 Catch Tampering Instantly
The cryptographic hash function at the heart of digital signature security is extraordinarily sensitive. When a document is signed, a mathematical fingerprint of the entire file is generated and embedded in the signature. Any subsequent change to the document—a single character altered, a comma deleted, a price figure modified, a clause reworded—produces a completely different hash. The mismatch between the recorded hash and the current document hash is instant and unmistakable. There is no threshold of "small enough to miss." Even a single altered character breaks the signature. Our tool surfaces this immediately, before the document is acted upon, filed, or paid.
👤 Verify the Signer's Identity
A valid-looking electronic signature is not the same as a cryptographically verified one. Anyone can add a drawn signature image to a PDF. What makes a digital signature legally meaningful is the underlying certificate—a cryptographic credential issued by a trusted Certificate Authority that binds the signature to a specific, verified identity. Our validation engine checks that certificate: who issued it, whether it was valid at the time of signing, whether it belongs to the named signatory, and whether it was issued by a Certificate Authority your system recognizes as trustworthy. Confirm that the signature belongs to who it claims to belong to—not just that a signature exists on the page.
⚖️ Legal Compliance Assurance
For documents where legal enforceability depends on signature validity—court filings, regulated financial instruments, HR employment records, procurement contracts, real estate transactions—an unvalidated signature is an unverified legal claim. Validation confirms that the e-signature meets the technical standards required for legal admissibility: an authenticated certificate from a trusted authority, an unmodified document hash, and a signature event that can be traced to a specific identity at a specific point in time. Check PDF signature validity before documents are filed, archived, or enforced.
📊 Full Certificate Detail Report
Beyond the headline Valid/Invalid/Modified result, our validation report provides the complete certificate detail: the issuing Certificate Authority, the certificate's validity period, the hash algorithm used, the signature timestamp, and the specific technical reason for any validation failure. This level of detail is essential for legal professionals who may need to produce validation evidence, for compliance teams documenting their verification process, and for anyone who needs to understand precisely what the signature check found rather than just its conclusion.
Who Needs PDF Signature Validation
⚖️ Legal Professionals
Court filings, affidavits, executed agreements, and legal instruments increasingly arrive with digital signatures. Authenticating those signatures before relying on them in legal proceedings is not optional—it is due diligence. Validate digital signatures in PDF documents to confirm they meet the technical standards for legal admissibility, verify that the signing certificate was valid at the time of execution, and produce a verification record that can be referenced if the signature's authenticity is later challenged.
🏢 HR Departments
Offer letters, employment contracts, onboarding documents, and separation agreements signed electronically need to be verifiably authentic before they become part of an employee's official record. Validating candidate and employee signatures confirms the document was signed by the right person, was not altered between signing and receipt, and carries a certificate that will hold up to scrutiny if the employment relationship is ever disputed. Verify e-sign authenticity as a standard step in your document intake process.
💰 Procurement & Finance Teams
Vendor contracts, purchase orders, invoices, and payment authorizations move large sums of money. A fraudulently signed vendor invoice or a tampered payment authorization that bypasses validation is a direct financial exposure. Before approving payment against a digitally signed document, validate the signature to confirm the document originated from the vendor it claims to be from and has not been modified since the original signing event. Authentication before authorization is standard fraud prevention practice.
🏠 Real Estate Professionals
Property transactions are among the highest-value agreements most individuals ever sign. Purchase agreements, deed transfers, disclosures, and closing documents require absolute certainty of signature authenticity. Validate digital signatures on real estate documents before proceeding to any stage of a transaction that relies on their authenticity. Confirm the document delivered by the opposing party is the document as signed—not a post-signature revision that altered terms you agreed to.
Understanding Signature Validation Results
Our validation engine returns one of three definitive results. Here is exactly what each one means and what to do when you receive it.
✅ Valid
The signature is cryptographically authentic. The digital certificate traces to a trusted Certificate Authority and is confirmed to belong to the named signer. The document's current hash matches the hash recorded at the moment of signing exactly—the document has not been altered in any way since it was signed. This document is exactly what it purports to be: a document signed by the named party, unchanged. Proceed with confidence.
❌ Invalid
The signature cannot be cryptographically authenticated. This result may mean the digital certificate is expired, was revoked by its issuing Certificate Authority, was issued by an untrusted authority, or does not correspond to the named signer. An Invalid result does not necessarily mean fraud—it may indicate an expired certificate or a non-standard signing tool—but it does mean the signature provides no cryptographic guarantee of identity or document integrity. Do not rely on an Invalid signature as legal evidence without further investigation.
⚠️ Modified / Tampered
This is the most critical result. The signature was once cryptographically valid—it was created by an authenticated signer using a trusted certificate—but the document has been altered after the signing event. The current hash does not match the signed hash. Something in the document changed after the signature was applied. This is a definitive indicator of post-signing tampering. Do not treat this document as a valid executed agreement. The signed version and the version you received are not the same document.
A Note on Editing Signed Documents
Our tool is built around verifying signed documents—but some users arrive here because they need to both verify and make changes. It is important to understand how these two needs interact.
Editing a signed PDF document will intentionally and immediately invalidate its digital signature. This is not a flaw—it is the security mechanism working exactly as designed. The moment any content changes, the document hash changes, and the signature hash no longer matches. The modification is cryptographically flagged. This is precisely what prevents someone from altering a signed contract and passing it off as the original.
If you need to make changes to a document after reviewing it, you can verify e-sign and edit PDF online easily using our connected tools. Use our Edit PDF tool to draft the revised version, then route the updated document for a fresh signature. The workflow is: validate the received version, identify what needs to change, edit to create the new version, and obtain a new signature on the updated document. This maintains the full chain of cryptographic integrity across every version of the agreement.
Complete Your Contract Workflow
Validation is the checkpoint. Here's what comes next depending on what you find:
If the signature fails validation, the document needs to go back for re-signing. Use Sign PDF to create a fresh, legally binding electronic signature on the corrected document. Draw, type, or upload your signature, place it precisely, and download a properly signed version ready for re-distribution.
If validation returns a Modified result and you need to produce a clean, agreed version for re-signing, use Edit PDF to draft the corrected document. Restore the terms as agreed, make any necessary revisions, and route the updated version for fresh signatures from all parties.
Document validated and ready to be filed for the record? Use Protect PDF to add password protection before archiving. Lock the validated, signed document from further editing. Preserve the exact version whose integrity you just confirmed—sealed and secured for the record.
Want to see exactly what changed between your original draft and the signed version you received—beyond what the hash check tells you? Use Compare PDF to generate a visual, line-by-line redline of every difference between the two documents. Cryptographic validation tells you whether it changed. Document comparison shows you exactly what changed and where.
Frequently Asked Questions
How do I validate a digital signature in a PDF online?
Upload the signed PDF to our validation tool. Our engine automatically reads the embedded digital certificate and computes the document's current cryptographic hash, comparing it against the hash recorded at the moment of signing. You receive an instant validation report showing whether the signature is Valid, Invalid, or whether the document has been Modified since signing. No technical knowledge required—upload the file and the report is generated automatically.
What does it mean if a PDF signature is invalid?
An Invalid result means the signature cannot be cryptographically authenticated as presented. This may indicate the digital certificate has expired or been revoked by its issuing Certificate Authority, the certificate was issued by an authority not recognized as trusted, the certificate does not correspond to the claimed signer's identity, or the signature was created with a non-standard or compromised signing tool. A Modified result—distinct from Invalid—means the signature was once valid but the document was altered after signing. Both results mean the document does not carry verified cryptographic assurance of its authenticity or integrity.
Can I validate an e-signature and confirm PDF document integrity for free?
Yes. Our tool performs a full cryptographic signature check—certificate authentication, hash comparison, tamper detection, and detailed validation reporting—at no cost, with no account required. Cryptographic verification of legally significant documents should not be locked behind a paywall. Upload your signed PDF and receive a complete validation report, free.
Is it safe to upload confidential contracts for verification?
Yes. All files are encrypted with 256-bit TLS during upload and processing. The validation process is fully automated—no employee ever accesses, reads, or reviews your documents. Files are permanently and automatically deleted from our servers immediately after your validation report is generated. Signed contracts, legal agreements, and sensitive financial documents can be verified securely without risk of retention or exposure.
What is the difference between a digital signature and an electronic signature?
An electronic signature is any electronic indication of intent to sign—a drawn signature image, a typed name, a checkbox click. It may or may not carry cryptographic verification. A digital signature is a specific type of electronic signature that uses Public Key Infrastructure (PKI) cryptography to mathematically bind the signature to a verified identity and the document's content at the moment of signing. Our validation tool checks digital signatures—those with embedded cryptographic certificates—rather than simple e-sign images, which carry no verifiable cryptographic credentials.
Will editing a document invalidate its digital signature?
Yes—immediately and intentionally. Any change to a signed document's content alters its cryptographic hash, causing it to no longer match the hash embedded in the signature. The signature is immediately flagged as Invalid on subsequent validation. This is the fundamental security mechanism of digital signatures: any post-signing modification is detectable. If you need to make changes to a document, edit it first using our Edit PDF tool, then obtain a fresh signature on the updated version.
Can I validate signatures on documents signed by DocuSign, Adobe Sign, or other platforms?
Our tool validates digital signatures that use standard PKI-based cryptographic certificates, which is the underlying technology used by major platforms including DocuSign, Adobe Acrobat Sign, and other reputable e-signature services that embed cryptographic certificates in their signed documents. Signatures created using these platforms that embed a verifiable digital certificate can be checked for authenticity and document integrity using our validation engine.
What should I do if validation shows the document was tampered?
Do not treat the document as a valid, executed agreement. Contact the other party to report that the version you received does not match the version that was signed—the cryptographic hash comparison confirms this definitively. Request a copy of the original signed document directly from the signing platform or the signer's records. If fraud is suspected, preserve all copies and consult a legal professional. A Modified validation result is objective, mathematical evidence that the document was altered after it was signed.
Ready to Verify What You've Been Sent?
Stop accepting signed documents on faith. Stop assuming the signature you see is the signature that was authenticated. Stop acting on agreements whose integrity you haven't verified.
Validate digital signatures in PDF online. Cryptographic certainty, instantly. Free, always.
Validate Your PDF Signature Now