The document discusses techniques for obfuscating malicious PDF files to avoid detection. It begins with an introduction to the PDF format and its object types. It then covers many obfuscation techniques like avoiding characteristic strings, splitting up JavaScript code, encoding strings and names, using uncommon filters, and introducing malformed formatting. The document also analyzes how these techniques can help files evade antivirus detection and complicate analysis by tools. It highlights the peepdf tool for its Python-based interactive PDF analysis capabilities. In conclusions, it finds that nested PDFs, compressed objects, new filters, encryption, and avoiding characteristic strings are very effective at evading detection.