Falsified or unauthorized modified PDFs are a real threat in professional settings. Altered contracts, fake invoices, or modified certificates can cause serious financial or legal losses. Here's how to detect them.
Common types of PDF falsification
- Text modification: An invoice amount, contract date, or important clause has been changed
- Page insertion/removal: Pages added or removed from a signed document
- Digital signatures removed or faked: The electronic signature has been deleted or replaced
- Metadata manipulation: Creation date or author changed to conceal tampering
How to verify PDF integrity
First check: digital signatures. A digitally signed PDF shows in Adobe Reader whether the signature is valid or whether the document was modified after signing. Green means confirmed integrity, red or yellow indicates problems.
Metadata analysis — clear clues
PDF metadata contains creation date, last modification, application used, and author. If you receive an "original contract" with a modification date more recent than the signing date — that's a clear red flag. DocInspector displays all these fields instantly.
Advanced hash verification
The cryptographic hash (SHA-256) of a file changes if even one bit is modified. If the sender provides the original hash and the received file's hash differs — the document has been altered.
Frequently asked questions
Can a PDF without a digital signature be verified?
Yes — metadata analysis, font inspection, and internal structure examination can reveal modifications even without a digital signature.
Are some PDFs so well falsified they can't be detected?
Advanced forgeries are harder to detect, but metadata and internal structure always leave traces. A thorough analysis rarely comes up empty.
Conclusion
Detecting falsified PDFs requires attention to metadata, digital signatures, and internal structure. Specialized tools make this verification fast and accessible to anyone working with important documents.