Add HTPBE? — forensic PDF tamper-detection API + web tool

[rogulia]

Link to the service, library or dataset

https://htpbe.tech/api

Category under which the entry should appear (select only one)

• Parsers, OCR and extraction
• Readers and viewers
• Creation and production
• Accessibility
• Datasets

(Closest existing fit — it sits alongside veraPDF as an integrity/validation tool rather than a generator. If you'd prefer to seed a dedicated Security & Integrity category, I'm happy to open a discussion with the rationale per CONTRIBUTING.)

Brief description of the entry

HTPBE? is a forensic API and free in-browser tool that detects whether a PDF was modified after creation by analysing the structural layer — metadata, xref tables, incremental updates, and digital signatures. It works without the original file. Suggested entry line:

- [HTPBE?](https://htpbe.tech/api) - API + web tool that detects whether a PDF was modified after creation by analysing the structural layer (metadata, xref tables, incremental updates, signatures).

[avvertix]

Ehi @rogulia thanks for sharing the service. I opened the pull request #30 to include your service, which I find personally interesting.

If you'd prefer to seed a dedicated Security & Integrity category

I see the point, for now I'm leaning to a Validation and compliance section that your tool can fit together with VeraPDF. This way we don't have a single entry section.