Simplify your workflow with aliases:
# Set an alias in `~/.bashrc`
alias htmltopdf="docker run --rm -v $(pwd):/converted/ arachnysdocker/athenapdf athenapdf "
# Reload
source ~/.bashrc
# Convert HTML to PDF
htmltopdf http://blog.arachnys.com/
Suppress errors (e.g. extension "RANDR" missing
):
# Redirect errors to /dev/null
docker run --rm -v $(pwd):/converted/ arachnysdocker/athenapdf athenapdf 2> /dev/null http://blog.arachnys.com/