One way is to use the "bitmap" client or some other bitmap-editor (e.g.
Sun's icon-editor tool, post-processed with pbmplus) to design the individual
characters and then to do some large amount of post-processing to concatenate
them into the BDF format. See Ollie Jones's article in the November 91 X
Journal for more information.

The R3 contrib/ area (in fonts/utils/ and in clients/xtroff) contained a
number of useful utilities, including some to convert between BDF font format
and a simple character format which can be edited with any text editor.

An easier way is to use the "xfed" client to modify an existing font; a
version is on the R4 or R5 X11R5 contrib tape in contrib/clients/xfed. Xfed
was last seen on ftp.Informatik.Uni-Dortmund.DE [129.217.64.63], possibly as
file /pub/windows/X/Diverse-X11-Sourcen/xfed.tar.Z. It can produce BDF-format
fonts which can be compiled for a variety of X servers.

IBM machines appear to have a utility "fontutil".

The xfedor client from Group Bull permits creation of bitmaps, cursors, XPM1
pixmaps, and fonts. Binaries for common machines are on avahi.inria.fr in
/pub; in addition, the sources (an old Xlib implementation) have been placed
[5/91] in ftp://ftp.x.org/R5contrib/.

If you are a MetaFont user you can use "mftobdf" from the SeeTeX distribution
to convert PK, GF, and PXL fonts to BDF format; the distribution is on
ftp.cs.colorado.edu and on ftp.x.org.

The GNU package fontutils-0.4.tar.Z on prep.ai.mit.edu includes xbfe, a font
editor, and a number of utilities for massaging font formats.

The O'Reilly X Resource issue #2 contains an article on using these tools to
modify a font.

Fonts can be resized with Hiroto Kagotani's bdfresize; a new version is in
ftp.cs.titech.ac.jp:/X11/contrib.  bdffont in the Andrew User Interface
System (versions 5.2.2 and higher) lets you create a font or edit an existing
one.