Mdtryhht

I want to create plots in Mathematica where all labels have font sizes which match those in a LaTeX document.
I start by defining

Needs["MaTeX`"];
texStyle = FontFamily -> "Latin Modern Roman", FontSize -> 12

Now, if I export a simple plot

Export["test1.pdf", 
 Plot[Sin[x], Cos[x], x, 0, 2 Pi,
 BaseStyle -> texStyle,
 ImageSize -> 400]]

the font sizes match those in my document. However, if I include a plot legend

Export["test2.pdf",
 Plot[Sin[x], Cos[x], x, 0, 2 Pi,
 BaseStyle -> texStyle,
 ImageSize -> 400,
 PlotLegends -> Placed[MaTeX["\sin(x)", "\cos(x)"], 0.6, 0.8]]]

the font size in the plot is too small. This might have to do with the fact that Mathematica makes the second plot smaller (independent of MaTeX).

This has nothing to do with MaTeX and is essentially a duplicate of

• How to export graphics in “Working” style environment rather than “Printout”?

(But can't be marked as such because that question is on StackOverflow, and it was asked before the creation of Mathematica.SE)

However, MaTeX does come with a nice tutorial on preparing figures to size, which explains this issue. Enter MaTeX/tutorial/PreparingFiguresToSize in the address bar of the documentation browser.

In short, when an expression with head Graphics or Graphics3D is exported, it retains the sizes. However, when any other visual expression is exported to PDF, it will use the styles from the PrintingStyleEnvironment. The default is "Printout", which downscales everything to 80%. This applies to all sorts of expressions that format content in notebooks, such as Row, Grid, Labeled, etc. It also applies to Legended, which is the head of any graphics containing a legend. This is because Legended uses the same underlying boxes as Grid, Column, Labeled and several others: GridBox.

Yes, this is very annoying and very hard to figure out if you are not aware of it.

The workaround is to set the PrintingStyleEnvironment to be the same as the style environment used for on-screen display:

SetOptions[$FrontEndSession, PrintingStyleEnvironment -> "Working"]

This setting will persist until you restart the Front End. If you use $FrontEnd instead of $FrontEndSession then it persists even across restarts. I do not recommend doing this though, as there is a good reason for the "Printout" environment downscaling to 80%: this environment is used when printing notebooks or converting notebooks to multi-page PDFs. Without the downscaling very little content fits on a single page.