This example demonstrates how the chemnum package can be used to automatically number compounds in reaction schemes created with ChemDraw (saved as .eps files). While the chemstyle/chemscheme package can also be used, its author recommends the use of chemnum as it's deemed to be clearer.
Ideally, the ChemDraw-generated .eps files should contain "TMP1", "TMP2" etc as temporary markers, which will then be replaced with automatically incrementing compound counters using the \replacecmpd command. Set your Overleaf project's compiler to be LaTeX (required for .eps images) when using this method.
This is an example document for the achemso document class, intended for submissions to the American Chemical Society for publication.
For more information on preparing your manuscript for submission to ACS Publications, please see their resource center.