Using epstopdf
This article concerns the
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If you wish to use the epstopdf package with Texpad, you must first enable the -shell-escape option of the typesetting pane of the Preferences window.

This is because epstopdf launches an external binary via \write18{}, which must be explicitly enabled when invoking TeX. This is because \write18{} allows for arbitrary code execution on your machine, which is a serious security hole. For obvious reasons we do not enable this by default.