AdobeFnt.db and FntNames.db files – don’t delete them!
People may suggest you delete the Adobe font cache files to attempt to fix certain problems – and indeed, under some uncommon circumstances, an Adobe font cache file may get messed up. These font cache files are AdobeFnt*.lst files (where “*” may be nothing, or may be a two-digit number).
However, there are two files with simjilar names, but ending in “.db”, which are not caches, are not subject to any kind of corruption that we know of, and should not be deleted. AdobeFnt.db and and FntNames.db are both static database files used by InDesign. Deleting them, especially FntNames.db, can cause serious problems.
So what are these database files?
“FntNames.db” is a database of menu name information used to give nice, long, friendly and typographically accurate menu names for old Adobe Type 1 (“PostScript”) fonts when displayed in modern Adobe applications. It looks up the font by the PostScript FontName.It is a plain text file, so it’s possible for users to edit it – though this is not recommended.
Assuming that deleting it doesn’t cause any problems launching InDesign, it would certainly cause a change in menu name handling, resulting in the font references in future documents (for Adobe’s Type 1 fonts) being inconsistent with everybody else, and even with your own past documents.
“AdobeFnt.db” is another static database file, this one for font and glyph metrics for font substitution of some common old Type 1 fonts when using Adobe Sans and Adobe Serif. I think it’s used by Acrobat and Reader. Although it could have been be used by Adobe creative applications in the past, I’ve been told it isn’t currently.
Although “AdobeFnt.db” is less critical than “FntNames.db”, deleting it certainly won’t help with the kinds of problems you’d be deleting the cache files to fix.