I have a font that I want to be marginally thinner. I've typed out the word and then added a white outline around it.
What I want to do is delete the outline, whilst maintaining the thinner font. How can I do this?
You can use the Appearance panel (shift+f6) to achieve this, and have your text remain editable. Select the 'characters' in the Appearance panel and then select Effect > Path > Offset path... and enter a (small) negative value for the offset. If necessary, you can expand (Object > Expand Appearance) the result in order to be able to edit it.
Alternatively, for earlier versions of Illustrator, you will have to convert your text to outlines (shift+ctrl+O; Type > Create Outlines) in order to apply the offset effect.
Do note however, that this is not the proper way of treating your typefaces. Typeface weights are designed with certain propotions and line widths in mind. You faking a 'thin' variant in this way is ignoring all the effort the typeface designer put into their design.
Therefore, the really proper answer should be: obtain the lighter font variant and use that.
Simply select the type with the selection tool.
If you then want the stroke as a separate object, choose Object > Expand Appearance from the menu
I do this quite often and as follows is my preferred way of completing this effect:
Select the text and click " Type > Create Outlines"
This will outline your text only but not the stroke!
To outline the stroke too click " Object > Path > Outline Stroke "
This will rendered the stroke and the text as outlined.
The two parts will be grouped together, ungroup these using " Object > Ungroup " (you will need to do this twice)
Now for the tedious part, select each shape that is part of the text and make this a compound path by clicking " Object > Compound Path > Make ".
Do the same for your outline.
Once done you can select both of these elements and you will now subtract the stroke from the original text making it your desired size.
To do this click " Window > Pathfinder " in the pathfinder toolbox click upon " Minus Front ", this will subtract the front shape from the one behind, leaving you with your lighter text.
Contrary to the techniques of simply placing a stroke above your text in a colour that matches the background, this allows you to place the text anywhere without the need to find a suitable blend with the artwork behind.
This technique can be utilized in many situations and it can be useful to start understanding how shapes work in groups and the rules of compound paths. I imagine you will encounter them a few times in your career and it can save you a good 20 minutes messing around if you are clued up on how to group, merge and subtract shapes from the get go.