I have not seen such a DLL, but I have written programs for small printers. I used the standard fonts of the printers. I found the explanations I needed in the programming manuals that I could donwload for free from the web sites of the constructors. These printers have their own languages. I saw ZPL and EPL. You write lines of comands in a file, and then send the file to the printer via FTP or another way. Here is a commented example in EPL:
; Set label width in dots
; Select print speed 50mm/s (medium speed) 1is low speed, 4 is high speed.
; Enable direct thermal mode
; Enable top of form backup
; Disable Windows command mode
; Printing from top of image buffer
; Set form length 1218 with a gap of 25
; Clear image buffer
; Select font 8-bit, first resident font
; Define the location, font, and string of characters to be printed
; reverse(N=normal),"text"(in quotes)
A50,62,0,5,1,1,N,"Test Ascii text"