PDF Tamper Detection — Find Out If Your Document Was Altered
HTPBE? is a PDF modification detection tool that identifies whether a document was altered after creation — free in the browser, with an API for automated workflows. Used to detect altered invoices, forged contracts, and tampered certificates. Receiving a PDF and have no original to compare against? See the no-original-file workflow.
The problem
Modern document fraud is invisible to visual review
A growing class of document fraud opens a genuine PDF, edits a balance, a date, or a beneficiary, and re-saves it. Visually nothing changes — the document passes pixel-level review, layout review, and KYC.
Structural PDF analysis reads the layers rendering engines never expose: revision history, object structure, signature coverage maps. That is where edits leave fingerprints they cannot wipe.
Common tampering patterns
- Modified balances or totals after export
- Swapped IBAN or beneficiary on invoices
- Post-signature edits on contracts
- Backdated issue and modification dates
- Fabricated documents from consumer PDF tools
What this looks like
What PDF Tamper Detection Looks For
Three real fraud mechanics we catch at the structural PDF layer.
Timestamp anomalies — the most common tampering signal
A PDF carries internal creation and modification dates. When the modification date follows the creation date by days or months on a document that should never have changed, this is the first and most common sign of tampering.
Known editing tool in the producer field
The PDF records which software last processed it. When the producer field shows a tool designed exclusively for editing existing PDFs — such as iLovePDF, PDF24, or Smallpdf — rather than the original document application, this is a strong indicator the file was modified after creation.
Incremental revision layers
PDF editors often append changes to a file rather than rewriting it. This leaves multiple revision layers that are invisible in a PDF viewer but detectable through structural analysis. Each additional layer represents a post-creation edit.
Removed or invalidated digital signature
A digital signature cryptographically locks a document’s contents. If a signed document is later modified, the signature becomes invalid. If the signature was removed entirely after tampering, that absence is itself evidence of forgery.
Producer mismatch across document generations
Genuine documents come from a single known producer — a bank portal, accounting system, payroll service, or IRS e-file. When the producer field in the PDF does not match the claimed source, the file was re-saved through an editing tool after its original issuance.
Font subset drift across pages
When a PDF is edited in multiple sessions — or pages are assembled from different source files — the font subset prefixes diverge between pages. This is invisible to a reader but a clean structural signal of composite or multi-session editing.
The detection gap
KYC platforms check the document. HTPBE? checks the file.
Two different checks — both matter.
KYC & identity platforms
Plaid · Persona · Alloy · Jumio
- Is this a real bank statement template?
- Does the account number match the identity?
- Is the document format consistent with the issuing bank?
Detects fake documents. Does not detect edited real documents.
HTPBE? tamper detection API
Structural PDF integrity
- Was this specific PDF file modified after it was generated?
- Do metadata timestamps match the file structure?
- Were digital signatures valid at the time of signing?
What HTPBE? checks
Detection capabilities
Deterministic structural signals. No probabilistic scores, no model training.
Producer signature mismatch
The PDF claims to come from one tool but the binary structure points to another. The first signal of post-export editing.
Incremental update trail
Every save after the original creates an incremental update. Long chains mean multiple editing sessions on the same file.
Multiple xref tables
Each editing session adds a new cross-reference table. Genuine institutional PDFs have one. Tampered PDFs have several.
Modification timestamp gap
A real PDF has matching CreationDate and ModDate. Months between them is a high-confidence forgery signal.
Digital signature validation
When a digital signature exists, we verify the coverage map. Modifications after signing return certain-confidence verdicts.
Font and object consistency
Edited text introduces new font subsets or objects with origin patterns inconsistent with the rest of the document.
Share with engineering
Wire this into your intake pipeline in under a day
Two API calls — one POST to submit the PDF, one GET to retrieve the verdict. Forward this page to your engineering team; the full API reference, quotas, and copy-paste examples in cURL, JavaScript, Python, PHP, Go, and Ruby are one click away.
Pricing
Self-serve plans, no sales call
All plans include the same forensic checks. Pick the quota that matches your monthly document volume.
manualStarter
$15/mo
30 checks/mo
Manual spot-checks and integration testing
most commonGrowth
$149/mo
350 checks/mo
Active document processing pipelines
high volumePro
$499/mo
1,500 checks/mo
High-volume automation and API integrations
Enterprise (unlimited, on-premise available) — see full pricing
API key on signup. Free test environment on every plan. No card required.
Customer Stories
Teams that stopped document fraud
Compliance, finance, and risk teams use HTPBE? to catch manipulated PDFs before they become costly mistakes.
Caught an invoice where the total had been changed by less than a thousand dollars. Without this I would have approved it without a second look.
Sarah M.
AP Manager
United States
We had three applicants in the same week with bank statements that looked completely fine. Two of them were flagged as modified. You simply cannot see this by reading the document — it is in the file structure.
Lars V.
Risk Analyst, Online Lending
Netherlands
Salary slips were coming with altered figures. We identified two problematic files before the placement was finalised.
Priya K.
HR Operations Lead
India
Since we started checking documents this way, we stopped two applications early in the process that would have been very difficult to reverse later.
Julien R.
Fraud Analyst, Fintech
France
Some applicants were sending PDFs that looked authentic but had been edited in ways not visible to the eye. We now ask for checked originals when something is flagged. Already saved us from a few bad decisions.
Marta S.
Compliance Coordinator
Spain
One invoice was caught because there was a mismatch between the document dates and structure. That particular case would have cost us significantly.
Tariq A.
Finance Manager
United Arab Emirates
FAQ
Frequently asked questions
What is PDF tamper detection?
Can I just check if this PDF was edited?
How do I know if a PDF has been tampered with?
Can PDF tamper detection catch all types of tampering?
Is PDF tamper detection free?
How do teams use PDF tamper detection in production?
Does tamper detection work alongside existing KYC, OCR, or AP platforms?
Secure your workflow
Create your account — API key on signup, free test environment on every plan.
From $15/mo. No sales call. Cancel any time.