How accurate is PDF modification detection?
Our PDF modification detection system provides high accuracy through multi-layer analysis combining metadata validation, structural analysis, and signature verification. The accuracy depends on several factors: the quality of PDF metadata, the sophistication of modification attempts, and the PDF creation tools used.
Results come in three states: Intact (no signs of modification found), Modified (modification detected), and Cannot Determine (the PDF was created with consumer software such as Microsoft Word or LibreOffice — integrity analysis does not apply to documents created with these tools).
There is one fundamental limitation to understand: the tool detects post-creation modifications, not fabricated content. If someone creates a fake invoice or certificate from scratch in Word and exports it to PDF, that PDF will show as Intact — because it was never modified after creation. The check only tells you whether the file was changed after it was generated, not whether the data inside it is truthful. See Can someone create a fake document from scratch? for details.
For critical decisions, we recommend using this tool as part of a broader fraud-detection strategy rather than relying solely on automated results.
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Our PDF authenticity checker accepts PDF files up to 10 megabytes (10 MB) in size. This limit ensures fast analysis and optimal performance for most common PDF documents including contracts, certificates, invoices, reports, and academic documents.
Files exceeding this limit will be rejected with an error message. If you need to check larger PDF files, consider splitting them into smaller documents or compressing the PDF before upload.
The 10 MB limit applies to the original file size before any processing. Our free PDF tamper detection service is designed to handle typical document sizes efficiently while maintaining quick response times and reliable analysis results for PDF modification detection.
HTPBE? analyzes four layers of evidence: metadata (creation and modification timestamps, creator/producer applications), file structure (incremental update sections, cross-reference tables), digital signatures (presence, validity, post-signature modifications), and embedded content (JavaScript, hidden file attachments).
What you see is one of three results: Intact (no modification detected), Modified (modification detected), or Cannot Determine (the PDF was created with consumer software such as Microsoft Word, LibreOffice, or a print-to-PDF driver). The detailed metadata and findings on the result page explain the reasoning behind each outcome.
Our PDF modification detection system can identify most common types of PDF alterations including:
- Metadata changes (creation dates, modification dates, creator/producer information)
- Structural modifications (xref table changes, incremental updates, object-level changes)
- Post-creation content modifications (page additions, object insertions, structural edits)
- Digital signature tampering
The most important limitation is not technical — it is fundamental: the tool detects modifications to existing PDF files. It cannot detect documents created from scratch with false content. If someone creates a fake bank statement in Microsoft Word and exports it to PDF, the result will show as Intact, because the file was never modified after creation. Always check the creation date and consider the document’s claimed origin alongside the analysis result.
Additionally, PDFs created with consumer software (Microsoft Word, LibreOffice, Google Docs, print-to-PDF drivers) will show a Cannot Determine result rather than Intact, because anyone can create any document from scratch with these tools.
Other technical limitations: password-protected PDFs cannot be analyzed, extremely sophisticated manipulation techniques using specialized tools may sometimes evade detection, and PDFs with corrupted metadata may produce unexpected results. For critical legal or financial documents, use our service alongside other fraud-detection methods.