Can I change the font or page-number placement?

Yes. The preset styles give you a coordinated starting point, and the formatter's settings let you adjust details on top of that — including the body typeface and the page-number (folio) placement (for example footer-centered vs. outer corners), plus options like running-head content and where numbering begins.

Change a setting, check the live preview, and re-export when it looks right.

Among the settings worth knowing about:

• Page numbers — top, bottom, or none; centered or in the outer corners; whether they print on chapter-opening pages; and whether numbering restarts at 1 on Chapter 1 with roman numerals for the front matter.
• Running heads — on or off, and whether they carry the title and author, the title and chapter, or the title alone.
• Chapter openers — how the number is written (Chapter One, Chapter 1, One, I, 1, or none), the title size, how far down the page the chapter starts, drop caps, and the chapter lead-in: the first few words of every chapter in small caps (or italic), the way most American hardcovers open. It follows the drop cap when there is one, and the first-line choices style the whole opening line instead of a few words.
• Body — typeface, size, line spacing, margins, justified or ragged right, and indented or block paragraphs.
• House style — under Curly quotes and proper dashes, one choice sets three rows: US (Chicago) sets the sentence dash tight (word—word), the ellipsis as three spaced periods (. . .), and double quotes outside; UK (Oxford) sets a spaced en dash (word – word), keeps the one-character ellipsis (…), and puts single quotes outside; As typed keeps whatever your manuscript does. Each row can also be set on its own. The same choice reaches the ebook and the manuscript export, so the three never disagree.

Six body typefaces are available. If your book uses unusual characters, check that your choice contains them — see Will my accents and special characters print?