In the Silhouette Studio® software program, you may use a Bold feature for fonts to thicken or widen the letter style. However, not all fonts have an option to Bold programmed within the font style. If the font in question does not have the option to Bold, the Offset feature can alternately be used (which is intended for making shadows for letters but which can have the same type of effect as thickening the letters).
Please click here for further information on the Offset feature for Silhouette Studio®.
A video showing the process is shown below: