What are the file size limits for PDF checking?
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.
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How accurate is PDF modification detection?
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How does HTPBE? determine whether a PDF was modified?
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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.
PDF authenticity checking typically completes within a few seconds for most documents. The analysis time depends on file size, complexity, and server load.
Typical processing times:
- Small PDF files (under 1 MB) usually process in 2-5 seconds
- Larger files (5-10 MB) may take 10-20 seconds
The multi-layer PDF tamper detection process includes metadata extraction, structural analysis, and signature fraud detectionâall optimized for speed. You'll see real-time progress updates during upload and analysis.
Our PDF modification detection service is designed for instant results, allowing you to quickly check document integrity without waiting. If analysis takes longer than expected, it may indicate a complex PDF structure or temporary server load, but most PDF authenticity checks complete rapidly.