Thanks to Michael Houghton <firstname.lastname@example.org> for the suggestion.
We previously decreased the bottom margin for paragraphs. This worked for the web version, but not for the PDF. Reverted PDF <p> margin back to 1.75em; changed HTML <p> margin to 1em. Now _everybody_'s happy.
Relative URLs for entries confused TwitterFeed.com, so we now use the full URL. Previously, the <updated> element of <feed> wasn't dynamic. Now it's set to the date of the most recent entry.
The newer frontmatter pages hadn't been added to the ToC, so added them. Fixed their appearance in the ToC so their page numbers displayed as Roman numerals.
Previously the pages preceding the recipes (Introduction, Convention, etc.) had standard page numbers, when they should have used lowercase Roman numerals. That is now fixed.