If you rename the file extension to .zip or .rar (or use a tool like 7-Zip ), you can often extract hidden files, source code, and auxiliary "goodies" embedded within the document's bytes.

When you download a file like GTFO.rar or a specific issue (e.g., pocorgtfo23.pdf ), you aren't just looking at text.

The archives are often mirrored on sites like The International Journal of PoC||GTFO .

No Starch Press has released multi-volume physical collections of the early issues if you prefer a tangible "long guide." PoC∥GTFO 23: Reverse Engineering Insights | PDF - Scribd