Generating a PDF using AsciiDoctor

I am trying out how to generate a PDF from my asciiDoc files. I ran "gem install asciidoctor-pdf" and it appeared to complete successfully (no error messages; ended with "21 gems installed"). However when I run "asciidoctor -r asciidoctor-pdf *.adoc", it completes with no messages, but there are no *.pdf files in the directory.

Am I doing something wrong, or are the PDFs written to another directory?

It appears I was using the wrong syntax. Running "asciidoctor-pdf *.adoc" did the trick.

Extending my question: How do I customize the appearance of the PDF?