The screen fonts distributed by Adobe have a slightly different character spacing than those distributed by Apple. Page 22 of the Adobe Type Library User's Manual points out:
"If you own an older Macintosh, not a Macintosh Plus, and are concerned about character spacing, avoid using the Bold and Italic selections from the Style menus of your application. Instead, install the bold, italic, and bold italic screen fonts available in your typeface package and select these fonts from your application's pull down menu when you need to change styles. You will then get more accurate spacing when printing documents."
The manual goes on to say:
"If you own a Macintosh Plus, you can install only the Plain font and still get correct character spacing. For display clarity, however, you may want to install the Other fonts."
If you are using a Macintosh with the 128K ROM's, only the Plain font needs to be installed. Just remember to use a Font/DA Mover of version 3.1 or later so the FOND resource is correctly installed.