Here is the entire code for my document:
\documentclass[11pt]{article}
\usepackage{graphicx}
\begin{document}
\includegraphics{image.pdf}
\end{document}
When compiling, I get the error
! Missing number, treated as zero.
EDIT: Thanks to Marijn for help with formatting.
EDIT 2: Bonus points to whoever can reproduce the phantom character.