[arivero]

An amusing experiment could be to investigate what kind of document files are supported and how.

For instance, rename your .pdf document to .txt or .aaa. Does it still recognised it as a pdf file? If so, they are using the 'file' instruction from unix.

Try exotic files: PERL, php, sh, py and so on. Does it recognise some of these? Then you have scripts.

Try HTML files containing javascript. Does it work?

Try different versions of .jpg .bmp .png .pgm and similar bitmap files, not only black/white