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Aperi'Solve v.3.4.1

pdfinfo

pdfinfo (from the poppler suite) prints the document-level metadata of a PDF: title, author, producer, creation and modification dates, page count, PDF version, page size and whether the file is encrypted. It is the quickest way to size up a PDF challenge.

What Aperi'Solve runs

$ pdfinfo document.pdf

The output is returned as a table of the non-blank lines.

Reading the output

Title:           Annual Report
Author:          alice
Producer:        LibreOffice 7.4
CreationDate:    Sat Jul  5 12:00:00 2025 UTC
Pages:           3
Encrypted:       no
Page size:       612 x 792 pts (letter)
PDF version:     1.7
  • Author / Producer / Creator — the tool that generated the file. A mismatch with the document's apparent origin, or a telling username, is a common early clue.
  • CreationDate / ModDate — timestamps that can order events or expose a file that was edited after it was "signed".
  • Pages — a blank-looking PDF with more pages than you can see hides content off-canvas or in a hidden layer.
  • Encrypted: yes — the content stream is protected; you may need the password (or a permissions crack) before other tools can read it.

Installing locally

$ apt install poppler-utils

The same package provides pdftotext, pdfimages and pdftk-style helpers for extracting the actual content.

Limitations

  • Reports only the document metadata, not the objects inside — for suspicious JavaScript, embedded files or auto-actions use pdfid, which also runs on your upload.
  • Malformed or truncated PDFs may report nothing; poppler is fairly lenient but not a repair tool.

Common CTF patterns

  • A revealing Author or Producer string, or a comment left in the metadata.
  • Extra pages beyond what a viewer shows, holding hidden text.
  • Encrypted: yes pointing you toward a password/permissions puzzle before the flag is reachable.