Choose the most suitable preposition to complete the sentence.

The emergency contact details are printed _______ the visitor handbook.

The correct answer is within.

Explanation:
The sentence requires a preposition that denotes the location of printed information inside a document or publication.

The preposition within means inside the bounds, contents, or limits of something. When talking about information contained inside a handbook, manual, report, or book, within (or in) is used to indicate that the text is printed inside its pages.

Let's analyze why the other options are incorrect:

1. beside: Means next to or by the side of something (e.g., "sitting beside the door"). Information is printed inside a handbook, not next to it.
2. against: Suggests physical contact or opposition (e.g., "leaning against a wall"), which does not make sense in this context.
3. through: Indicates movement from one side to another or from beginning to end (e.g., "walking through a tunnel"), which is unsuitable for describing location within text.

Therefore, within is the most appropriate preposition to complete the sentence correctly: "The emergency contact details are printed within the visitor handbook."