fontforge software package provides font editor, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install fontforge
fontforge is installed in your system.
Make ensure the fontforge package were installed using the commands given below,
$ sudo dpkg-query -l | grep fontforge *
You will get with fontforge package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Fonts |
| Package | fontforge |
| Version | 20120731.b-7.2+b1 |
| Description | font editor |
| Sub Section | Fonts |