When you're working with an invitation, you can select specific characters and adjust the horizontal or vertical spacing. When you're working with addressed envelopes, the placeholder address on the front of the envelope will be replaced with names and addresses from the customer's Address Book. In order to adjust kerning on addresses, you can specify individual kerning pairs and the amount to adjust the spacing. To adjust the kerning for an envelope, double-click on the placeholder address on the envelope and click on the Kerning tab in the Edit Text Box window:

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You can add up to 8 kerning pairs for each envelope. To add a kerning pair, click the Add button. In the kerning pair, you specify the first letter, the second letter, whether to tighten or loosen the pair, and the number of pixels to adjust the spacing.