Signed distance field rendering is a technique that allows render bitmap fonts with crispy result while upscaling.
If you have not heard anything about this before, please, read this libgdx article.
For creating distance field font you can use littera.
For usage this amazing trick simply change style property on your TextField or Mesh:
textField.style = new SignedDistanceFieldStyle(4.0);
Constructor takes one argument - spread this value depends on distance field bitmap creating and define edge sharpness, just change it if you want to make edges less or more smooth.
Feel free to edit this part of the page if you want to add information that's lacking in the above description.
Questions are better asked in the forum, though.