When you would select any barcode font in any of your application package, the code would appear on the screen, and you can print it out as part of your document. What could be simpler? The main problem is that your word processor will try to print the code no matter what point size type that you specify.
An important thing that needs to be addressed is that the smaller font size you may employ, the higher the resolution of your printer must be to render the code properly. If you have a font, such as Code 39 installed, try generating a code using a 10 point type and printing it on a 300dpi laser printer.
By using a magnifying glass, you can view the code, with a view to check the width of narrow bars with the width of the narrow spaces. They should be equal. If your printer is like mine you'll conclude that the bars are about twice as wide as the spaces. This would not be an acceptable code.
Thus to avoid, this sort of glitches to take place, you may require to use any Barcode Printing Program. There are barcode applications, which wouldn't print a code unless a narrow bar is at least three dots wide. For example, on a 300dpi laser printer each dot is 0.0033 inches in diameter (1/300). Three dots would be 0.01 inch. So, I shouldn't print a code on a 300dpi printer with a small bar less than 0.01 inch wide. If I use fonts the printer will try to print any code I tell it to.
In order to ensure the best result, let us see some samples of print codes. Get some barcode prints for trail, and look it by employing your magnifying glass. Again, look at the narrow bars and narrow spaces. Their width should be equal. Find the smallest point size that you can print in and still have them equal.