When framing pictures, if you plan on using glass, you absolutely must mat the photo using mat board. This is because an emulsion pressed straight to the glass will tend to, especially in humid environments, adhere to the glass.
Side note: Please allow your printed photos time to air out before placing behind glass as well, as the dyes do "breathe" and can adhere to the glass if you print and frame immediately.
A signed mat board is somewhat commonplace now for wedding photos.
Now, for something more professional looking, you can run a mat board through a printer (be warned, you need a printer that can run paper through flat and it may take a lot of trial and error to figure out profiles).
Hiring someone adept at calligraphy is also an option, as is using a set of stamps (a-la letterpress printing). A custom decal or sticker could also be used.
IMO - the best looking option is calligraphy.
Now, if you want to go super cheap - you can load your image into Photoshop or Gimp and create a fake mat and add the text to it. Have the whole thing printed and framed (don't use glass for reasons above).
I've done a lot of faux mats for budget high school senior photos. Some can look pretty good. But, they simply can't touch a physically matted and framed, museum glassed photo.