Unlike MS Word, InDesign won’t let you “fake” a bold or italic style where the type itself doesn’t include a bold or italic font. It will allow you to slant characters, but designers consider that to be bad form. Discussion of terminology of typography may help you understand why.
When people speak of fonts, they are typically using the word inaccurately. Here’s the truth:
- a typeface is the name of the font, also referred to as a font family. Examples are: Times New Roman, Helvetica, or Arial.
- a font is a rendition of the typeface, for example, “Arial Italic 14 pt.”
Historically, the term font is derived from the words, “fount” and “foundry,” brought forth from the printing press era when type actually came from blocks of metal or wood. At that time, each character was a physical object; therefore, each was manufactured in a specific size and shape. Print houses organized these fonts by family names. Because of this process, each typeface designer created separate versions (i.e., fonts) of his/her typeface – and they still do so today. As a result, true italic and bold typefaces are not just slanted or thicker; they have their own unique characteristics, which look completely unlike their “faked” counterparts. See: http://desktoppub.about.com/cs/typestyles/a/italics_2.htm.
In practice, the faked ones (e.g., the ones you get by clicking the Bold or Italic buttons) may not print. Although your desktop laser printer can print your slanted or fattened versions of fonts, commercially used offset printers may not understand the computer-fabricated versions. Since it is best not to risk expensive proofing, the temptation to “fudge the font” is eliminated in InDesign.
To supply further reasoning: font designers are artists, and they get royalties for their work. Generally, you purchase typefaces by individual font style; adding any of the type’s children (which may be italic, bold, etc.) is optional and involves additional cost. In this way, the font “artist” receives royalties for each purchase.
For all these reasons, in InDesign you can’t do something that seems so easy. Consequently, if you don’t find your favorite typeface in italic, you’ll just have to choose another typeface.