To map fonts, edit shxfontmap.txt using a text editor. This file resides in the following location: %APPDATA%AutodeskRevit
For each TrueType font to map, add a line with the following format:
filename.shxFontname
where:
  • filename.shx is the name of the AutoCAD SHX font to map from
  • is the TAB key on the keyboard
  • Fontname is the font to be mapped to
Save and close the file.

You do not need to restart Revit for the font mapping to take effect.

Via
https://twitter.com/RTVTools/status/458699381047173120

Read more / copied from: http://knowledge.autodesk.com/support/revit-products/learn-explore/caas/CloudHelp/cloudhelp/2014/ENU/Revit/files/GUID-87119589-ADE4-41AD-A796-3EB3C1DDDA82-htm.html

“In Revit, the default font is Arial, for example, is therefore the DWG file represent fonts in Arial.
The “shxfontmap.txt” is located at:
C: Users AppData Roaming Autodesk Revit Autodesk Revit 2013
First you should make a backup copy of “shxfontmap.txt” are created, they can then be opened with Notepad.
Note: Please do not use software to edit the file, which could change the formatting of text, such as Word.

At the end of the file is then added to “txt.shx Arial” or “Arial italic8.shx” added.

After the names of the SHX once is “Tab” and then use the new font specified.”

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Autodesk BIM Blog – Darstellung von SHX Schriften f�r DWG Dateien anpassen – Revit Architecture/MEP/Structure 2013