GREGORIO is a handy instrument for typing up Gregorian chant. While installing the software can be daunting, Source and Summit have an Online Editor called the Illuminare Score Editor. It has a handy web interface to process the GABC code which Gregorio uses to produce PDF or EPS files.
GABC files can be downloaded from Gregobase for the majority of chant in the Liber Usualis and other staple books of chant. This is a fantastic aid to making printed choir materials.
However, the more keen eyed publishers will want to adjust the spacing sometimes. The way to do this is not very obvious, leading some to resort to Photoshop or Inkscape to make adjustments.
Here is an example:
(c4) A(g) test(g) case(g) (:) to(g) add(g) more(g) space(g) (::)
Firstly, you can add extra blank syllables, either
~( ) or just
( ). The tilde appears in the preview but is rendered as a space in the PDF or EPS output.
(c4) A(g) test(g) case(g) ~( ) (:) ~( ) to(g) add(g) more(g) space(g) ( ) (::)
If those spaces are too big, you can use a tilde
~ to give a more subtle space.
(c4) A(g) ~test(g) case~(g) (:) ~to(g) add(g) more(g) space~(g) ( ) (::)
Or if you want even more space, you can add
( / / / ) with as many slashes and spaces as you need.
And here is a screencast I made while figuring this out.