PDF Tamper Detection — Find Out If Your Document Was Altered
HTPBE.tech 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.
What PDF Tamper Detection Looks For
Every PDF carries hidden evidence of its history. Here is what to look for.
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 Easy Way: Use HTPBE?
All checks run automatically in seconds — no technical knowledge required.
Upload your PDF
Drop any PDF up to 10 MB onto the checker. No account required.
Tamper detection runs automatically
All detection layers — metadata, structure, signatures, and content — run simultaneously in under 3 seconds.
Get the modification detection result
A clear verdict — modified, intact, or inconclusive — with a plain-language list of every finding.
Frequently Asked Questions
What is PDF tamper detection?
PDF tamper detection is the process of analyzing a PDF document’s internal data to determine whether it was modified after its original creation. It examines metadata timestamps, file structure revision history, digital signature integrity, and application fingerprints to identify signs of tampering.
How do I know if a PDF has been tampered with?
Upload it to HTPBE. The tool analyzes the PDF’s internal metadata, file structure, revision history, and digital signatures — all in under 3 seconds. If the file was modified after creation, the analysis returns a “modified” status with a plain-language list of specific findings.
Can PDF tamper detection catch all types of tampering?
No automated tool catches everything. HTPBE reliably detects the most common tampering methods — metadata editing, incremental updates, signature removal — but sophisticated forgeries that rewrite the entire file from scratch may not leave detectable traces.
Is PDF tamper detection free?
Yes. The web tool is completely free with no upload limits. No account required. API access for automated tamper detection workflows starts at $15/month.
How do teams use PDF tamper detection in production?
The most common integration is a pre-verification step at document intake. When an applicant, vendor, or claimant uploads a PDF, the API returns a structured verdict before the document reaches a human reviewer. Lenders use it on bank statements and payslips. AP teams use it on vendor invoices. Claims ops use it on repair invoices and medical bills. Every verdict is deterministic with named structural markers suitable for an audit trail.
Does tamper detection work alongside existing KYC, OCR, or AP platforms?
Yes — it is designed to be additive. Identity-verification platforms (Persona, Onfido, Alloy) verify the person. OCR platforms extract data. AP automation routes invoices. None of them analyze the structural integrity of the PDF itself. HTPBE adds that layer at the document level without replacing any existing workflow.
Pricing
Self-serve plans. No sales call, no procurement process.
Starter
$15/mo
30 checks/mo
Manual spot-checks and integration testing
Growth
$149/mo
350 checks/mo
Active document processing pipelines
Pro
$499/mo
1,500 checks/mo
High-volume automation and API integrations
Enterprise (unlimited, on-premise available) — see full pricing and docs
API key on signup. Free test environment on every plan. No card required.
Who uses this in production
The same detection engine, framed for the teams that rely on it.
Alternative Lending
Bank statement and payslip forensics for lenders — structural PDF layer Plaid and Persona don’t provide.
Invoice Fraud
Detect altered vendor invoices — swapped bank details, inflated amounts, fabricated suppliers.
Insurance Claims
Tampered repair invoices, medical bills, and proof-of-loss PDFs flagged before payout.
Detect PDF Tampering — No Reference Copy Needed
The no-original workflow: how to detect tampering when you only have the document you received, with no reference copy to compare against.