Getting psfrag to work in pdflatex

An example using the pstool package to get \psfrag commands working with .eps images in pdflatex. There's a caveat; after the initial compile, if you add more \psfrag or change the replacements, it doesn't auto-update the replacements in the PDF output on Overleaf unless you do a recompile from scratch, or the .eps file itself is updated.