This should have been a relatively painless process. Tex up the
paper, tar up the source files. Upload and submit. Easy. Unfortunately not, MNRAS doesn't accept PDF's that have "Type 3" fonts in the PDF - type 3 fonts are bitmapped fonts. Type 3 fonts have been around since 1984 but apparently because of some printing problems for MNRAS and the fact they can look ugly on PDFs on screen (apparently) they are a no-no. 

Anyway for the last day or so Type 3 fonts have been my nemesis. The first time I tried to view my uploaded PDF on the MNRAS website I got the error message saying the problem was "most likely" with the type 3 fonts and I should add some font tricks to my Latex preamble to fix it.  Various recommendations they suggested were to use \usepackage{times} and/or  \usepackage[T1]{fontenc} and/or \usepackage{aecompl}. Now that's fine and all of those packages will likely produce Type 1 fonts in your PDF file. However, after I inserted some of the suggestions and checked the fonts used this time in my pdf file I got this...

The second column is the font type and that helpful first column is the name. Yeah. The Type 3 fonts remain. So I tried pretty much everything to convert the Type 3 fonts to Type 1 fonts. Nothing works. The problem is that the type 3 fonts, as I discovered after some trial and error, are embedded in the .eps files I was using within the document. Now the good news. You can convert these with a little bit of magic. What would have been really helpful is if that had been mentioned on the MNRAS website. Given I imagine lots of people use matplotlib to create figures then lots of people are probably creating files with Type 3 fonts. So what's the magic? Well, first - try to identify which eps files are using Type 3 fonts. I'm not sure of an easy way to that except by moving through the latex source and setting \end{document} after each figure and compiling and running pdffonts on the result to check when you start seeing Type3 fonts.


Once you have identified the source of the problem you can run
gs -sDEVICE=epswrite -dNOCACHE -sOutputFile=<Filename> -q -dbatch -dNOPAUSE <Input Filename> -c quit on the bad eps file, replace those eps files in your document and you are done. Running pdffonts now should give something like...

and now you are done!